You're going to need a lot of minerals, so start hoarding them now. Even manufacteuring simple ammo can easily deplete what you have. The nice thing about it though is that you can essentially do three things at once with this career choice. Research a blueprint to improve it, manufacteur something, and strip mine the local asteroid belts including the veldspar because you will need massive amounts of tritanium regardless of source.
You definately want to see about raising your refining and mining skills. You could skip the mining skills if you have someone else reliably doing it for you or even if you don't mind a slower rate but the refining is absolutely crucial. Whether you mine the ore yourself or buy the ore from someone else it'll give you the best yeild. You could just buy the minerals but that can be expensive as well as not be entirely reliable (ie you buy everything available and there's nothing left or what is left is so expensive it's not worth it).
So try to get refining, industry, and research up to lvl 5, and throw in mining if you want as well. After that you have more options to choose from and it becomes more what you want to specialize in. Weapons research and building? Ship research and building? All of them? There's pretty much a skill for each category plus a few that are required by more than one. So at this point look over the skills available and see what appeals to you most.
Now as for a starting point, you definately want to start somewhere small. You won't get much profit but it won't cost you much either. Ammo and small weapons is a good place for instance. Everyone needs them so you're almost guarenteed to sell. When you do sell them, be sure to check the market first and not just sell them. You can normally get a lot more for a sell order than you can by the quick and fast way. For example the lowest sell price can be say 6isk for a unit of lead ammo. There are people out there with a buy order for 0.01isk for a unit of lead ammo. If you just sell it the fast way, you just sold it for 0.01isk per unit. Setting up a sell order is easy, the small fee is barely worth mentioning and can be reduced through the trading skills (another area you may wish to look at), and you can control how long you want the order to stay there (I normally do it for a week, long enough for people to see it but not so long that I have to go and cancel it if I need to, you can do whatever you feel is best though). Normally with the small things though, I usually end up having sold them within a few hours. It takes longer to make the stuff than to sell it.