Where I live (Southeast Asia) renting is about USD20 a day for the full set. If you're doing at least 2 trips/15 dives a year I would say that's reason enough to buy.

As far as trying gear goes by renting, it's tricky because you might just go through a string of the same equipment (for example here almost all shops rent Scubapro T-one or Mares Rover jackets), unless you actively seek out shops that have different gear to rent. If there is a club or something similar near you, perhaps that's one place you can go to try on other people's gear.

Suit depends very much on your personal tolerance to cold. Rent a 5mm and see how you feel. Thicker wetsuits are harder to put on and move in so you may want to think about a drysuit instead of a 7mm.

One thing that may influence your regs is whether you want to dive doubles in the future, as not all first stages route the same way. Also how much clearance for your head? And the G260 is a very popular second stage but is heavy, so when I do S-drills it droops and looks hilarious.

I went computer & mask > fins > bpw > accessories (lights smb cutter etc) > wetsuit > regs > drysuit