I turn most 1st to 3rd level spells into Gambits (which anyone can do, but incurs penalties if you fail a check to do them perfectly) or Adventuring Gear.
I then create four tiers of skill proficiency -- Untrained (raw ability), Proficient (PB), Expertise (double PB), Mastery (take 10 + double PB). I also make it so you can FoRK (fields of related expertise) Expertise into Untrained and Mastery into Proficient skill/tool checks (boosting it to Proficiency or Expertise) so long as its a shared ability score root or both are tool checks. Lastly, I expand skills from 12/13 to 16. This creates a dynamic skill game that isn't complex and has way better function IMO then the current one.
Lastly, martial classes get guaranteed magical items whenever they get an ASI. Sorry, but D&D is about Fighters with magical gear, not Tom with just a club. That club has killed so many orcs that now it burns with mystical flame near them due to being bathed in their hatred, etc etc.
Wizard also becomes the Intelligence skill monkey, with Bard being the charisma and dex skill monkey, and Rogue being the any-skill skill monkey (most masteries, master of FoRKing).
The gap left by hollowing out 1st-3rd level spells is replaced with more class specific spells so that every spellcaster has a huge number of actually cool magical class-specific stuff, not naughty word like Longstrider and Jump.