I have an off brand mountain bike that has a 3x7 drive.  I really don't need all those gears.  I mainly ride on the road and treat it as more of an urban/ town bike.  I will never use it on a serious trail.

One of the issues is that as much as I tune it,  I can't seem to get it to stay in proper gears with out double shifting. And since I pretty much ride exclusively in the mid gears, I was thinking about the swap. I  even took it to a bike shop and they tuned it, but was back to missing within a week.

I reached out to the distributor and they said the Deore was a fit.  I'm not looking for high end and this is a budget bike.

The only real downside I've heard people talk about is that 1x's work the chain and teeth more,  and that could cause more wear.

I also have to figure out how to identify the hubs and bracket specs.  

Thoughts or ideas would be appreciated.

All bikes outside of high end units will need constant tuning. Every time you bump a derailuer you will need to tune it. Or un tweak it, but that requires decently expensive tools too.

I converted a bike to 1x before, but honestly you could just as easily leave the chain in the gear you want and just leave it. A front derailuer shouldn't start rubbing out of nowhere if you're not shifting it. I've also seen some people just buy a down tube shifter and rig it to the seat tube and use that to control the front derailuer so it doesn't require tuning as often due to cable stretch.

All said another way...what problem do you have that you think a new group set would fix?

Budget build: Micro Shift Advent for derailleur, shifter and rear cassette, Buckloos 1x crank set and a KMC chain. All from amazon. You'll likely need a new free hub wheel, my go to is Modernbike.com.

all in will be about $250.

No important reason,  just thinking simpler and less moving parts is always better.

I really only ride in gears 8-14

The lower end drivetrains are really finicky and easy to knock out of alignment, fuck front derailleurs.

That being said, learning how to tune them is not hard if you're mechanically inclined, I would suggest Park Tool youtube videos. It can be done with simple hand tools.

That being said (lol) no regrets with 1x systems.