I love Tuscany, Its the Prussia of the Mediterranean with the Italian peninsula's outstanding basetax and of course the twin universities and great idea that can put you miles ahead of other nations.
1469 is great to have a dominant position in central italy like you have, Don't bother with rome unless you need the money or trade power its better to vassalize the pope instead and get the free core then use the saved Admin points to pop your stability after the pope asks for it back. Don't worry about Milan, they will die eventually just make sure France and Austria stay out of northern Italy. Meanwhile if Naples breaks out of thier unions, devour it, wholesale then release sicily and get the free cores. Whenever you get the chance even for -2 stab try and vassalize Tunis it comes in handy if you eventually colonize.
Your going to need to determine exactly what you want to do New world is possible but you need to move your capital, To either Antwerpen, or Seville for europe (One of which requires some wars inside the empire and the other is a straight up war with spain) or into the new world. Genoa is terrible for colonies in america since it doesn't get any trade from it.
If you want to go for africa, Stay in Firenze or move to Venice. Or Rome (because its Rome!) Make sure you knock tunis out and keep spain the hell out of Morocco and west africa or they'll suck up all your trade which you will need to support colonies there. Beat up on mali every time the truce runs out until thier gone, free goldmines and alot of free tradepower provinces in Timbuktu. Then its up you where you want to go after you reach the cape.
Asia you should move capitals to Venice, its just a better trade node than Genoa in every way except of course being where most of your land right now is located. but that should change. Becuase Venice in any way you take should be your primary rival, Vassalize them as soon as you can and hold them so Austria doesn't take any of their stuff. If the ottomans want some of the islands, just don't bother defending them unless youve got the navy or Austria's willing to beat them up for you. Once you have Venice your going to want to beat up on the Ottomans and Mamluks and then everything from India to Japan is yours for the taking.
If your going to Europe then Austria becomes a liability, your friends should be France and ironically the Ottomans. Mainly becuase of Austria who will oppose you at every turn if you take practically anything that speaks german. Take the Alps, and try to get your capital out of italy (trade flows out of italy from europe not into it unfortunately) then work on dismantling your neighbors, even your allies. Becoming Italy is arguable if you want to end the game as the HRE go for it, if not pass, Tuscan ideas are generally better though Italy does get a cool flag.
So in short, pick a direction and kill everything that isn't paying you trade money. then go back and beat up the other countries for thier money while your at it. Your tuscany you'll have better ships, better men and better cannons than everyone else by the time the reformation ends, and if you stay as a republic you'll be able to choose for free every eight years what points you want to bring in and be able to make up the difference with advisors.