When you say first team, do you mean first XI?
If so, Alisson, VVD, Trent, Robbo, Fabinho, Mane and Firmino cannot be improved upon imo by practically anyone (many would add Salah here, I think he's replaceable). That leaves Matip, two midfielders and possibly Salah.
If you replace Matip, Gomez doesn't get a look in as he'd be 4th pick so he'd want out. I would argue that Lovren/Gomez are already the best 3rd/4th choice CB options from any European team right now. Salah wouldn't settle for a rotation role so he'd want out (he's already been hankering for a move to Real or Juve anyway).
Midfield is the only place we can realistically improve imo.
I agree with improving the first team and the squad will take care of itself...to a point. When you're first XI is as strong as ours though, that's damn hard to do so you look to improve the supporting cast meaning you can rest the odd player without a major drop in performance. Backups. That's our big weakness.
No, a "first team" isn't eleven players nowadays. I mean the squad. We should always have options in every position. Competition for places is a good thing

