Wendy's doesn't have a ton of gluten-free options- particularly if you're celiac- but what it has is fine. Chili, baked potatoes, and frosties are all gluten-free, and the way they are prepared presents low to no risk of cross-contamination even if the staff doesn't take any direct steps. I frequently get all three from this location, and haven't had any issues. Salads are trickier; I've not gotten one from from Wendy's, but it seems possible to order them in such a way that they'd be GF.
There are no GF sandwich options. Don't bother.
— Not very
— Separate gluten-free menu
— Not Much