what would be the 'best' way of not gimping yourself completely?
Pick one class ... and play it as that one?
I would start as Barbarian, create regular Barbarian ... and then started adding things, focusing on buff and utility spells like Shield for Wizard or Armor of Agathys from Warlock.
Barbs can't cast spells while raging, so I don't think Shield works great there, though Armor of Agathys would be cool.
To not gimp yourself, I'd start with 2 levels of Fighter for Action Surge. Any class can use the extra action, especially since BG3 doesn't limit spells per turn.
