ok, well the titles pretty self explainitory, but what subfolder in the data folder would i place pcx and tga files in?
They go to the dustbin of history, never to be spoken of, heard of, or seen any more.

Read
this thread for a more comprehensive explanation.
When you switch to DDS files (or PNG in case of interface files), you should then tell us what type of textures you're using. If they're effects, the go to /MOD/data/effects/, if they're ship textures, they go to /MOD/data/maps/, if they are interface files they go to /MOD/data/interface/.
Knowing what purpose you're using the textures for is sort of integral to telling where they should go.