The folks before me decided to save $100 by building a nice metal shop right at grade level. It also happens to have a pretty nice sized area directly up hill. Building is about 25' long on the uphill side where the water is coming in.

Any suggestions on how to best fix this? I have a tractor with a bucket. Should I just dig down until I'm 4-6" below the slab all the way around and give it a slight contour back to the original grade? Channel Drain?

Agree with building berm uphill to redirect water away from building.
Route water into a shallow 8' to 10' wide swale to carry water away from building.

Gutter the building and use 4" SDR PVC ( green schedule 35) on downspout- buried to route water away from building. Or collect building water into very large rainwater tanks.

Previous two posters pretty much said what I was going to say.

Slope away from the shed then build a swale uphill to divert the water around the shed.

Agree with above, of course

V-shaped uphill berm redirect and if it fails, then research dam building methods that go deeper and fight erosion failures

Gutters 6-in, leaders/downspouts at least at building corners .... will make foundation work better (thirsty exposed corners tend to droop in clay/other supporting soils w/o extra watering in summer) ... leader end feed into 10ft long tubes away and downhill but could be perforated at corners (see above)

This is why Navasota now requires a licensed Architect or Engineer to design metal building/barndo foundations, as cutting foundation cost corners is how they have brought the price/sf down to temp buyers -.... I am told. Maybe OK in sandy areas but not in clay soils.

This is in Milam county, haven't dug many holes but seemed like 18" of sand and some clay underneath