Also what decides a horses value? I have been selling all of them for $1000 but idk what they're actually worth?

You have mostly very low value horses that arent likely to sell for anything. Its recommended when starting out to not take on too many horses at once and focus on a few to career them for money and train them up to higher levels and PS. The only decent one is the quarter paint thats level 64 but I dont know a ton about them to know if it will sell for 7k

Thank you! I will Foucault on training and lower my prices for the ones I have.

An alternative you could consider is keeping the low value horses (since you've already bought them) and using them solely in hoofbeat plains (Explore > Hoofbeat Plains).

If you were to do this, don't bother with training, showing or using them for career. Instead use all of their energy in explore. You can catch wild horses which often have great stats and sometimes rare coat colours. The wild horses can sell really well or you can use them to show / breed your own lines (which can be easier than starting with foundation horses). Remember there is a 15 min cool-down after you catch a wild horse before you will be able to catch another.

You can also find seasonal dyes, treats (food) and other items in explore (like whistles and, very rarely, breed coins). These can all sell really well too. I personally don't waste energy collecting lassos, roses or plain dyes as these are not really worth anything.