Regular PVC cement will literally weld the 2 PVC parts/fittings together. The "weld on" brand I think you're talking about should work fine, as long as its for PVC (not for acrylic or anything else). The cheaper stuff is fine though, and weld on is more expensive. I doubt you even need PVC primer along with it unless your actually putting real pressure into the system. You can usually get away with just the cement in low PSI plumbing applications like hydroponic systems, and its not like anyone is gonna inspect it. they do make clear primer though, which is what I use instead of the purple stuff.
Anyway, the solvent in the cement literally melts and rapidly expands the parts into each other to form the bond. The pipes and fittings are made to be tight interference fits, and need to be held together for a good 10-20 seconds before letting go for it to work.. otherwise the fittings will pop right back off if you let go too soon. You want to spin the pipes or fittings together when possible as you push it in, to assure you have cement all the way around with no gaps.
You can't just use the cement like glue to adhere blocks or whatever to each other, not very good anyway. Gotta be a tight fit, which most PVC plumbing parts are made to be. Its more like welding with chemicals than a glue or adhesive.
If you can take a good pic and show me what parts your trying to put together I can help. You can probably get away with using something else like adapters or clamps instead of cracking open a new can of cement just to glue up one joint..