It all comes down to how much you want to spend, the size of your studio and the type of clients you are targeting. Once you have figured these things out then it will be easier for you to make the right choices. But I would suggest you look into kettlebells, medicine balls, battling ropes, TRX, jump ropes and exercise bands if your budget is limited. And you don’t need a large number of any of these items in order to create a great program for your clients.
I hope this helps. Good luck!