Having just finished a Spain game without ANY form of cheating to enhance my nation (as I was going for as many achievements as possible so I had no choice), I would probably write this game off as a bad debt and start a new one.
What I did in mine - to add I'm NOT in any way a good player of this game in comparison to many on here so if I can do it YOU most certainly can - is as the start to knock the early sliders on towards Free Trade, take the Church Attendance Duty NI and get the "Gilded Iconography" cultural decision as that is ridiculously powerful. After you've got that switch to take the trade NIs, you'll lose 3 stability but trade like a madman as much as possible and channel all that gold into bumping your stability up to +3 again. This will give you the financial means to raise a few armies to protect yourself.
Early on you start on very good terms with the Catholic nations so cultivate those, especially Aragon, Portugal, and France. That way you save having to build massive armies to conquer them and concentrate on a good size army simply to smash Grenada and annex them. This should really be your only military annexation on the European mainland. Once they've been absorbed, take your maintenance sliders to say 15 to 20% for rebel hunting, keep them there and keep charming your neighbours with gold. Get Royal Marriages with Portugal and Aragon in order to later claim their thrones with the goal of eventually inheriting them. Perhaps don't RM France as the drop in relations you get when you claim the throne of another nation you have a marriage with is costly to build back up, but by all means try for an alliance. With luck and a few goes at "Claiming thrones" you should be able to peacefully unite Iberia under the Spanish crown, could also do the same with England/GBR after if you like but as I hate Monarchies in general in the game, I switched to Republic as soon as I formed Spain.
Once done, the new world is yours to colonise for a long time before anyone else shows up as you've absorbed most if not all the major colonisers of the game
. Plough all monies into the Trade Tech (and grab a Trade Tech advisor if you can - you should have a high cultural level due to the gilded icon decision you took early on) to get QFTNW and start colonising the Canary Islands, Cape Verde and Azores first, building them up to cities before moving on. Once they core, go for the tip of Brazil to get an easy port for your exploring ships to get back to while exploring the Caribbean. Discover and colonise the whole Caribbean but DO IT SLOWLY, say five at a time maximum, no-one will race you there.
When you have say five colonies building, mint a little, just to stop you dropping into negative ducats at the end of the year but without gaining too much Inflation. Hire as higher star Master of Mint as you can and plop him in to fight the (low) Inflation you're generating. From there I would say you wouldn't really have to worry about money again. Just keep colonising slow and easy and you should get to the stage where you can have colonies on the go and it wont really make a dent in the money you're making to spend as you please.
Oh I should say once you start colonising the Caribbean, you'll run into the Aztecs/Mayans on the Mexican mainland, just load up with say 10,000 solders in a transport, only then raise your military sliders to 100% take them over and wipe the floor with them. (Take note to drop the maintenance back down afterwards - easily forgotten I can assure you) What I did was take all provinces on the east coast, leaving them the west coast, for three reasons, 1. So you can start wars in the future and keep milking them. 2. Once pirates come along theres nothing more annoying than having to sail around the whole of south America just to kill pirates that are taking your hard-fought provinces money. 3. So that once they core it gives you greater range to expand into both north and south America. Just absorb the Native countries later on when you've peacefully colonised up as far as you can without running into some native civilisation.
As a Catholic nation I'd advise keeping good relations with the Pope just to cover your backside and get cardinals that all help lower your badboy rating that you do get from running these wars but pretty much as long as France is on side you can do whatever the hell you want and learn the rest of the game safe in the knowledge you probably wont have as many money and inflation problems as before.
Just another thought, you'll probably want to go more towards Mercantilism the more you colonise as Badboy kills off trade in foreign COTs, and if you go the whole way in having both Americas you wont need to trade in another foreign COT again. Plus also you get a few nice Trading Decision pop-ups once you go Mercantalism.
Good Luck, I hope my long-winded diatribe helps somewhat! :rofl: