So as I mentioned, playing to figure out what to do and such is key. Here is a playthrough I just did where despite having every minor country around me except QQ and Kazan as vassals (including Nogai, or instance) the game is basically lost because of failing to follow one of the rules I suggested to you above ->
Georgia - dead man walking
So despite having good force levels and vassals like Greece that took religious ideas and is converting everything to Orthodox and such, in the last peace, I gave Muscovy a province next to Nogai without thinking. Since Nogai is my vassal, Muscovy was suddenly furious because it now wants every Nogai province in sight and Georgia's 200 relation with Muscovy dropped first to 40 at which point in mere seconds the alliance was dropped following by setting Georgia as a rival.
Now here's a key difference beyond that error on my part. Poland did not get a PU with Lithuania. Thus, having an alliance with Poland doesn't do very much (Lithuania rivaled both Muscovy and Georgia). Moreover, Poland decided to make Muscovy a rival and thus dropped the alliance with Georgia.
So, now Georgia, despite eating up most of the Golden Horde, giving most of Crimea to the vassal Greece, stomping Nogai and making them a vassal, is now, essentially, dead.
Without a strong alliance with a Poland + Lithuania PU (the latter cleans up the negative relationship with Lithuania by making it irrelevant), and with Austria still being too far away to ally, Georgia now faces hostile forces on all sides, with the Timurids having an alliance with the Ottomans, there is practically no chance for Georgia to continue growing in any direction.
So, as you can see, the strategy I suggested can work. However, when it comes to a country like Georgia:
1) weak
2) isolated potential western european allies worth having
3) surrounded by heretic nations that will naturally ally against them
*any* mistake can basically end your game and any undesirable events or non-events (i.e. Poland not taking a PU with Lithuania) can sink your campaign.
Thus, if you are new and learning, Georgia is probably one of the harder countries to choose from and you may want to start out with a country that has better chances
I'm rather enjoying Georgia myself however, as it presents an interesting challenge and breaking the code on alliances is one thing. The next thing to figure out is what optimal aggression consists of.
I discovered that with a Russian and Polish alliance, I could make Trebizond a vassal and get away with it. Note that you'll probably have to do this by force as they will ally with Circassia and when you take Circassia, you can take Trebizond.
Likewise, something I did was a no CB DoW Gazikumukh. I took Gazikumukh and made them a vassal ahead of attacking and annexing Circassia. I chose this order because having Gazikumukh rebuild their army gives a 5 stack early on that is very useful.
I also found that having a diplomat, I was able to do the move on Gazikumukh and take Circassia and Trebizond and still get a marriage with Muscovy and alliance thereafter. The timing on this is very important and getting Poland in a marriage and alliace is the first thing to get thereafter. You can reverse the order on these is one thing I found (I did a bunch of restarts to figure out marriage+alliance versus AE and found that AE wasn't a big issue for taking all 3 countries).
The combination of these two was enough to basically cause the Ottomans to go hunt elsewhere all the way up to the screenshot (see link at start).
Next, taking quantity ideas was key. By getting 1 level ahead of QQ and having a +discipline adviser with the +50% manpower, the combination of vassal armies and my manpower hit a point such that it was possible to stack wipe Shirivan (they will end up a vassal of QQ in almost every game it seems) and the remaining force numbers were thus sufficient to take QQ down, take Shirvan as a vassal and grab 3 provinces from QQ.
However, *before* doing this, I took Muscovy into a war against Golden Horde and created a land bridge to Muscovy with provinces reaching up to Muscovy (I gave him 1) creating a single province border (this became a small amount of border friction).
Thus, when I stomped QQ, key was that Muscovy could come in and fight. Thus, if someone strong had come in to help QQ (in a previous start, the Ottomans allied and joined QQ rather late into the war and I didn't have a land bridge to Muscovy - this late joining thing is very annoying).
So key was that with my strong ally (Poland dumped me before this point), the Ottomans turned up their noses and went west to go fiddle around in the Balkans some more.
So an important point here is that you should constantly watch for the right force structures and opportunity from a DoW versus who you will be fighting, standpoint, all the time, looking for the right moment to smash whatever country is currently your most dangerous opponent. Breaking the back of QQ gives Georgia a free hand for some time because Timi and the Ottos will proceed to clean up QQ's other provinces for themselves.
Your next low hanging fruit for aggression once you've gotten as far north and west as you safely can without ending up in a huge war is to go for Timi. By the time you've secured horde lands and QQ, Timi should be about ready to explode into a bunch of small countries and Persia due to revolts. You'll want to watch closely for the black lined provinces to start showing up and key an eye on Timi's manpower. DoW'ing on multiple countries, one at a time, after Timi starts to fall to pieces can give you the Persia trade node which is very rich. You may even want to move your main trade province to be in the Persian node as the Crimea historically doesn't easily go into high double digits without a whole lot of investment.
Ultimately, you will want to decide whether your main goal is Constantinople itself or controlling trade elsewhere.
Constantinople has so many trade lines going into it that getting it to >100/month without trade ideas can be done through conquest. This is, to me anyway, unique, because this is normally only the case for end trade nodes. Taking the Persian node and lands further and further to the east once you've secured your other borders seems best. Constantinople would be better in terms of ducats but that means not only fully stomping the Ottomans but defending Constantinople from everyone else that would like to have it. Thus, you must decide over time whether to fully commit more so East versus west. This is important because to get into big blob territory in the middle game, you will need to focus Georgia in 1 direction. The provinces surrounding Georgia just aren't very rich in anything - taxes, manpower, trade power are all pretty weak and you go through a *lot* of work to get these. So you won't be France's rival in the first 100 years (no doubt a better player could pull that off, but I don't see it normally being the case). So you will really need to pick 1. East seems best and going West seems more risky. The call is up to you of course.
Beyond that, if you go East, continuing to push through India gives you control over trade routes to buff up your Persia node and at some point you may want to take trade so as to redirect everything you can to Persia.
Also, in the case of Eastern Tech, Westernization may not be necessary. I had no trouble keeping parity with other Eastern techs and thus easily surpassing the Muslim techs. It's not likely as deep as Georgia is into the East, that a big Western power is going to show up to stomp them. So Westernizing or not seems fairly optional.
Another thing about Georgia - the national ideas are just awful. The buffs are mostly ones that don't really do much to help Georgia grow and thrive - survive a bit longer maybe, but not much more than that. Generic NIs are better than what Georgia gets.
You picked a very non-trivial country
