As Sam said, you can get most of your PVC stuff locally as long as it isn't too weird. One thing to make sure that you get good, if you're going to do a Herbie, though, is a gate valve. It is not the same as a ball valve.
https://www.bulkreefsupply.com/spears-gate-valve-slip-x-slip.html ... Yea, it's $50 but trust me, it'll be worth it when you want to dial Herb in and make the tank nice and quiet. If you don't care about a little noise, you can go cheaper, but ... get the fifty dollar one.
I use Rain-R-Shine PVC cement. It's bright blue, so I can tell if I forgot a joint right away. It also cures underwater and when wet, which is a plus. Make sure you dry fit your PVC fittings, and make sure you dry fit them properly. None of that "I mostly pushed it in and everything fit, and now it doesn't, what gives?" stuff. Its tough to get stuff apart, but worth it.
Invest in a good PVC cutter, too.
I also try to figure out where stuff will leak if it leaks. If it doesn't matter and its low pressure, I may not even glue it -- stuff inside the tank? Forget it, who cares!
I also position my bulkheads likewise. If I can (not always, but if I can) they're positioned over an open area of the sump. Not only will it minimise the risk of drips later, but when you need to eventually change a bulkhead, you just unscrew it, drain the overflow into the sump directly below, and go. No messing around with trying to maneuver a bucket into there.
Lastly, and most importantly -- if anyone tells you to glue your bulkheads, they're a moron, you should ignore everything they ever say, and you should use your ratcheting PVC cutter to ensure they no longer can pass such defective DNA onto future generations.
