Hey bud,
I'm a fairly new player my self, bought Vic2+AHD off of steam 2 weeks ago. I came from playing Hearts of Iron 3 a lot, so I had no idea how to manage all the little intricacies there are in vic2, just like you. But I just read a lot of AAR's, and they really helped.
So anyway, I'll help out with what I learned so for, so maybe others can correct me on some stuff.
Try to place your national focus in regions you need them the most. So if you need clerks in an eastward province of your nation, place a national focus there. You can
pretty much place them anywhere, there isn't any exception as far as I know.
Factories are something I'm not 100 percent too sure about; however, it's pretty important to understand what kind of factories you build and where you build them. So if you've got a lot of timber as a raw material produced in your countries, find the province that produces it a lot and place a lumber mill there; maybe down the road build a furniture factory in the same province. Basically, build factories that take advantage of your province's raw or produced goods (ie, if you're building a lot of lumber, and have tropical trees in the same province, build a luxury furniture in the same province). Also, it's very important to build railroads as they really help out with the output of your factories and rawgoods.
As for tariffs, I try to maintain it low, in case if my factories need to import materials, the price for those imported goods aren't too high to make my factories expenses go too high and close down.
As for warring for lands and colonizing. Just check what kind of raw goods they got, and see if it benefits you. Colonizing is always good since it can give you access to materials you might not find in your home land. It comes down to what you want for your country.
As for reforms, it all depends on your population and how you treat and spend on them. For example, if your population has a high literacy rate they will be more conscious about the government, and demand for reforms. Usually, if the population doesn't get what they want, they will rebel and force your political party to give what they want. Lastly, picking which political party impacts how often you can reform things; just read what stuff the party supports (ie, are they in support of laissez faire, state capitalism...so on). As for what kinds of political parties are the best, it all comes down again to what YOU want out of your country, and you'll figure that out by playing the game more.
How to tell if you are doing it right...well, the objective of the game is be #1, so it largely depends on how your country performs compared to the rest of the world. But, it's also fun to set personal objectives for yourself, and see how that works out. Like, invading Great Britain as USA, or being the #1 industrial nation without a big army.
Finally, the best advice I can give to you is just to play and experiment with the game first hand. It's certainly a lot more intuitive than just reading.
I hope that helped.