If he's tripping a lot something tells me may be his toes are too long.
That was my problem too till I switched the farrier: old guy didn't take enough toe off my qh and she was tripping badly, new guy does and it improved a lot. Pics of his trim would help tremendously.
If he ouchy on gravel (and usually you can tell that) then I'd consider boots. I personally keep pair of boot for each horse, but rarely put them on (only in very rocky parks).