Hey I need to know what's a good amount of tc to use as captial to start marketing, and how to determine the value of flame textures.

I'm not sure really what you mean but from 1tc, in a few days you can get up to 100k+ if you are a good marketer.

For flames, the price is determined on who made, the body part and the type of flame. If it is a wing flame, a cape etc...There's probably more to it than that but I'm not one with the market sorry. ;)

You can always ask someone from the market squad.
Check prices here: The Price Check Megathread.
Ask Questions here: General questions and queries