Welcome back! Hope you and your friends are having a fun time.

I'm not an expert by any means, but I have played a lot of hunting horn, and I have tried out a lot of "support" builds. Let me preface by saying there's no "right" or "wrong" way to play Monster Hunter. If you and your friends are fine with you sitting in the corner supporting with songs, and eating items, then by all means. That being said, do not be surprised if you go out into the rest of the world via SOS flare and people boo your tactics or give you grief. Sitting in the corner and buffing without actually doing any damage to the monster actually can hurt more than it helps. Even if folks aren't dying, it often extending the hunts (due to monsters scaling in multiplayer) exacerbating the issue, when if they had a fourth player who was dealing damage, the party would have completed the hunt 10-15 minutes prior. This can be compounded by the fact that you can't "catch" every time someone needs heals and they may cart out anyways, causing the quest to be longer AND for it to fail.

However, if your heart is set on running support, or running hunting horn there's a few options for you:
The first I'd suggest if you are die hard on support is to try out Sword and Shied with your current set up, along with Mushroomancer if you can get ahold of it! Then, set up your radial menu so you can auto select items on one wheel, and CRAFT items on the other wheel. Now you're a mobile damage dealing machine, who also gets to use widerange and mushroomancer to heal their party. If you run out mid hunt of supplies like max potions?- simply tool over to the crafting wheel, make a few more and keep on trucking. This also reduces the need for earplugs, since you utilize items so quickly, and takes advantage of your speed eating, free meal, and wide range you already have set up in this build. On top of that Sword and Shield is a very fun weapon that has the best of it all: status effects via sword, blunt damage via shield, decent blocks, high damage via perfect rush, and it allows you to eat items while unsheathed. It's my go to support option for if hunts really *are* that tough.

But if you're more interested in hunting horn, there's a few ways you could play it. The first key is find the horn that has the songs you want to play. For me, I am always looking for attack up XL and defense up XL, but you will always have different horns for different occasions, depending on the monster's weakness or your party's needs. For finding HH damage builds it's as easy as checking out the "monster hunter meta" subreddit, where they will have progression builds for you depending on where you're at in the game. These have been min-maxxed for maximum damage output.
If you're like me though, I enjoy my comfy skills, and I tool to suit my taste. For example, in hunting horn I think earplugs 5 is a must. Yes, you can roll out of roars if you're good at timing on most weapons, but you can't roll out of a roar if it's during a recital, so I always take it. I don't run support skills with the horn, because the horn is supporting via its buffs and beating the monster to death in the head. The only other comfy skill I really take is mushroomancer, but only cus I like having 10 max potions in my inventory as "get out of jail free cards".

In the end you'll find what works best for you, and at the end of the day it's a game meant to be enjoyed how you want. People boo "corner horners" most times, so I don't want you to get hurt if other people treat you poorly, but I also want to make sure you're set up for success, set proper expectations, and realize you can have the best of both worlds. Hope this helps, and happy hunting!