Congrats on transitioning! Right now I'm 9 months post relaxer so I'm still learning but am definitely available if you have any questions. I agree that you should look over fotki's for regimens, I honestly don't know if I could have transitioned without them.
During your first few months I would buy a few staples, loulou82 hit dead on the ones you need right now. Try to refrain from buying a lot of products just because your hair goes through a lot of changes and products that work well on hair with little NG don't always work as well as you get more NG. I barely use any products I bought when I first started transitioning.
Also if you can stay away from heat as much as you can and try low manipulation styles. I now see why so many naturals bun it, wear twists and roller sets, its the best way to retain hair while transitioning. I wear twists under a wig now and have minimal shedding compared to when I tried to wear my hair flat ironed when I first began transitioning and experienced lots of shedding.
Your relaxed ends need extra care so make sure to keep them moisturized and seal, I wish I knew when I started transitioning just how much this is important because if I did I may not have needed to cut so much of my ends off when I BC. Also pay attention to any changes in your hair in terms of shedding, breakage, ect to try to stop it before it gets any worse. I noticed a little breakage one week and by the next had extreme breakage.
A few staples I love(I'm a 4A/4B) that I've seen naturals on the board use are Cantu Shea Butter(great leave in for twists or to use as a leave in), QP Mango Butter (very thick without feeling greasy), ORS Replenishing Pack (great DC that feels great on the hair), Giovanni 50/50 shampoo, Kenra Moisturizing Conditioner (I swear by it as my staple conditioner), Hawaiian Silky 15-1(just started using it and almost kissed my bottle when I saw how soft it got my NG), a wide tooth comb and a Denman brush to help with detangling if that becomes an issue. Moisture is your best friend right now, good luck!!!