I would grow ALL the plants. I have 2 3x3 flower tents and currently running 12 per tent in 1 gal pots. I am planning on cutting back to 9 3 gal pots. Personally I would start with one to get your feet wet. You shouldn't waste a bunch of cash you won't get back. Pick up a reasonable light (I have a very nice set up on OfferUp if you're in phx ;-), a real set of nutes, at least a 2 gal pot, some bagseed, a small block of coco and go to town. You can expand from there, or if it's not for you, you can get out of it for most of what you got into it for.
I agree with @Icemann420 2 plants in there would be great, at least each plant gets its own 3x3 space, a good 6-8 week veg with a screen above would get you a great yield depending on the lighting, im currently running a 3x3 with 4 plants in but i had a short veg but i am considering a 1 plant grow in there soon, while i set my others away.
Hope this helps buddy and remember all of us here at are more than happy to help along the way!