Pretty much any Pokemon you want. They will generally be legit unless you specify an illegal moveset.
Specify:
- Level
- Item
- Moveset
- IVs/EVs if you know this, otherwise will be rand IVs and 0 EVs
- Shiny/Non-Shiny
Fair price is set at:
10 fg per standard Pokemon
15 fg for EVs/IVs distribution for competitive battling.
20 fg for unreleased events like Genesect, Victini with V-Generate, Zoroark wth Bark Out.