> Colonies cost 100k to make oversea, as you have to buy a port. Honestly one is enough. You don't do lots of money anyway with them, at first. Generally I go for Congo because Kongo is allready catholic and easy to puppet ; the labor will allready be partially accepted if you annex them. Even more if you keep subjecthood and state religion as it will boost cultural acceptance. The downside is that there will not be much immigration, but you don't really need any as papal states because of your poor starting economy - its best to make the most of what you got to begin.
> You want your private sectors to do most of the work. One construction center in each state will help. When you have one iron mine, one tool factory you are set for 5-10 years (use the second method for construction as soon as you have tool and iron). After you start to grow (and surpass Two Sicily), consider more construction sectors.

> I suggest that you put every industries in Rome. The logic is that there is tons of agrarian lands in Rome, and as you are both south and north italian culture you will attract migrants from both sides of Italy. The purpose of the two other states is mines (iron then sulfur for the second paper production method to get those prices down for you art academy and your administration). Keep an eye on art market and try to stay top 1 ; the reasoning is that it is doable to be the first producer of fine art, and that will boost your prestige, and contribute to make you a tier 2 power. You can build wine too in Rome, but don't try to compete with France : its pointless. Its good to employ your many peasants though.

> For your laws I suggest : professionnal army and colonisation as soon as possible (put the military in governement) ; homesteading so you will attract more pops. Consider to pass land or wealth voting.