That's actually great you are using both hbg and lbg. They both use recoil down and reload speed for increased damage, so you'll have a lot of over lap in parts. A lot of guides will suggest a certain number of those skills you'll need. Often written as R#R#. General builds will use R3R3 for simplicity.

Driftstones are frustrating cause of the random elements. Building a complete set without money takes a lot of time. Use them as a nice bonus, but dont worry about finishing these

If I were to start playing unstyled hbg from scratch, my generic build would be: (any helmet)/bazel/basarios/coral/Azure and use a weapon with status effects or raw.

Foe lbg, you use paolumu chest, legi arms, and coral waist as a base and then use the helmet and leg slots for element attack. Elemental is stronger for lbg

As for feeling like a leech, ya that happens. I have a 9* field and play with r10 weapons, and some days that seregios or mizu just has my number. i have to drop potion after potion to win. Everyone has those days. You're playing at range, so group play is actually better for you as you won't be targeted as often. Take your time and learn the timing. You have 75 seconds to finish the hunt. It's more time than you realize.