Once you discover mortar fireworks, nothing else will do.
The fireworks I grew up with were self-contained little packages. You'd light a fuse on a box or stick, it would do its thing, then be tossed. Mortars are different. A basic package contains a reusable launch tube and several shells.
A basic cardboard launch tube and eight double-break shells. The "double break" part means each shell produces two colorful bursts in the sky.
Drop a shell in the tube, light fuse and get away. Then, do it again. They go way higher, look better and make a bigger bang than other fireworks. They're really just smaller scale version of the stuff the pros use.
Industrious pyros line up multiple tubes, run fuse between them and launch several shells at once. Even more industrious pyros use pipe to make their own tubes for more simultaneous launches. This is where things can go sideways.
The tubes in fireworks packages are generally dense cardboard or fiberglass. It's easy to think that if cardboard would work, PVC from your local hardware store would too. Don't make this mistake. If something goes wrong and the shell explodes in the tube, shrapnel flies. Here's what that looks like:
Instead of PVC, professionals recommend High-density polyethylene (HDPE). It's much less likely to maim or kill someone if something goes wrong. Check out the difference:
A final note, don't be fooled by "ABS" pipe at the hardware store. It looks like HDPE but it's different and also unsafe. You're best bet is search online. (The top search result that came up me was PyroBoom which looks like a great place to start.)
Be safe out there and have a happy 4th of July.