Please, do not order Booster Kit, because it contains a lot of steel channels and those should be avoided. Competitive robots use aluminum parts with very rare exceptions.
This thread talks about alternative foam floor tiles: Cheap Alternative Tiles
Also, there is some additional cost saving discussion here: VEX Cost Reductions
You don’t really need full field. 8-12 floor tiles and a couple of game objects (cubes) will be plenty at the beginning.
The most important tools are T15 star screwdriwers and 11/32 wrenches that are available from 4" Zip Tie, Red, 100 pack - Robosource.net
Edit: moved itemized https://www.robosource.net parts to my previous post