This is location based but if you are in southern Cal I recommend usedgymequipment.com . They have a great selection of refurbished equipment. I’m assuming you are talking about a real gym and no a minimalist training studio.
I just purchased some refubished equipment for the Gym Store. I highly recommend them. The equipment arrived in like new condition. It was shipped very securely. And the cost saved me about $2500 dollars over the next lowest price that I could find.
A couple more suggestions would be Kettlebells (there are many exercises you can perform with just 1 kettlebell) and maybe a battling rope (if you have space for it).
I agree with Debbie, the TRX is a great machine, at not too much cost. I also think that the Total Gym is a good piece of equipment. Lots of great exercises with a minimal investment.
