Sorry a little late coming to this conversation. Equipment all depends on what type of MMA gym you are going to have. i.e. will it be an MMA gym that is also a fitness facility...
3 Octagons may be a bit excessive but then again I don't kow how many pros/amatuer fighters you will have at your place. If you have the space a ring would be awesome due to the fact you may also be able to attract a lot more pure boxers to your gym which would give your guys a great advantage from a stand up perspective. Kettleballs are a fantastic add to any MMA gym. Also as someone else said tires. Great for flipping and also doing sledge hammer drills on them. Also look into some plyometric type equipment. Muay Thai pads, focus mitts, double end bags, uppercut bags and interval timers are all great additions if you have the budget.
Good luck with your gym venture very tough fickle business...
Yes I decided to go with the 2 Octagons (1 30' and 1 22') and then 1 22' boxing ring. I will also have the pylometric and kettlebells.
