Most FG bikes at that price point are pretty much the same, it seems. Maybe check out State, Pure, 6KU. If you can save up and increase your budget a little, Kilo TT is a solid choice. Building your own bike is pretty much always going to be more expensive unless you have a lot of parts laying around. Number one tip: make sure you get the right size frame.

Read Sheldon: https://www.sheldonbrown.com/fixedgear.html
Also this guy, not my fav, but has some good beginner informational stuff: