Personal safety gear $1000-$1800 Helmet, Suit, socks, balaclava, arm restraints.
Do you want to just go out and race or do you want to be able to grow and be really competitive nationally?
Do you already have a tow vehicle or is that also part of the budget? Bigger car you will need a bigger tow vehicle. Is that part of your budget? Trailer, comes with the car or buy separately.
You can get a formula vee starting 5-6k and get something pretty competitive nationally(depending on your driving) +-10k. Seasonal rebuilds $1400-$2000/ 8 races. Tires, run up front nationally every other weekend, being a regional driver 6-8 races, or buy take offs from the national drivers for a discount. Very compettive class. Realisticly expect to budget a minimum of 1k/weekend for all the expenses at a minimum for any racecar.
Be honest with yourself about budget for year. Include rebuild, crash damage, storage, consumables (tires, plugs, brakes, lots of little stuff that adds up). Race weekend: tow gas, race gas, hotel, meals (you and crew), dues for non-member crew, entry fee, tolls, etc. Accesories: fuel jugs, speed jack, tools, pyrometer, tire pressure gages, other cool necessary or extra items. Not to mention the things you forget and have to buy another at the track or the local hardware store.
Fords will be more expensive. IT can be cheap or expensive. Formula cars are generally easier to work on and to fix crash damage. Full body cars can be harder to work on and are more difficult and time consuming to repair crash damage.
How fast to you want to go=how much money you have.