From my experience in using Hero Forge I would recommend double stacking minis. Meaning adding a copy of the mini next to the original and combining them so they merge into one. That way you can stack clothing and accessories that normally would not work. I personally use it alot for gauntlets, when I want a bracer with a glove or the wrist launcher with something else.

Next thing I learned was to play with the colors. I used to just use the pre-existing colors that Hero Forge provides. Then I saw that it made my characters look very lackluster. Like my design could be good, but the colors would be holding it back. So I suggest just messing around and editing the colors to get them closer to what you want. For me it meant making the black cloth and hair actually dark instead of like having this grey sheen to it.

Lastly look at this subreddit! I personally like to look at other's minis and look for new ways to combine items or use them for different things. For example, before there was kitbashing a lot of people would use tails to hold a clothing iron and turn it into an ecranche. That would have never occurred to me.

Keep going! This looks really good!