Since Kyle and I had the Exploration Set rather than the Remco collection, we didn't have a belt to store our gear. I nabbed the strap from my binocular case (which served as my "tricorder" before the model kit appeared) and threaded it through the hollow shell. It was just about long enough and thus resolved that issue. But the phaser and communicator, that was another story.
We'd usually push the grip through a belt loop. That actually positioned the gun similarly to what we saw in the show, but it was prone to sliding and falling to the ground. We wound up snapping off "emitters" and having to re-glue them. I usually just carried the comm' in my hand or stashing it within a pocket. Kyle tried rolling a length of adhesive tape into a "tube" with the sticky surface facing outward, applying it to the back of the comm' and slapping it to his belt to be a bit more authentic. Yeah, it usually pried loose from any movement.
Uniforms? well, Kyle initially had a light brown pull-over with a dark collar. Looked pretty decent as a "command" department tunic. I had a blue turtleneck, but it was almost navy rather than a mid range blue. Kyle had black pants, but I had to settle for beep brown. Kyle had some brown boots he tried turning black two different ways. One time, he got a roll of electrician's tape and "mummified" the footwear. Another time, actually tried to spray paint them!
Later, Kyle and I discovered shirts being sold at JC Penny's with starsip chevrons. They didn't have rank braids but rather black elastic cuffs that matched the collar. I think I read that they were sold as sleepwear. But dang it, to have an arrowhead breast patch that wouldn't dislodge (as we had used cardboard gripped with tape) was paradise! we could "forgive" the cuffs.
Sadly, about the time we had collected our somewhat more authentic ensembles, we both moved to different parts of the state and I didn't find anyone else with whom I could "pretend".
Follow-up: Ah, I see ssosmcin and I discussed the same clothing. I did a wee bit of Google-fu and learned DonMoor made those cuffed Trek shirts.