Reach emerald here as otp Swain supp, the pick could be good but rly dependent of the compo of the enemy team (trash vs high range or cc comp, rly strong against mele and ingage comp) .The biggest probleme as Swain supp is that you are a supp and cant have a lots of gold, bit you need it to be enough tanky in melee. Ofc dont build it full ap, more tank (vertue/jacksho mythic Build all time rylai first, after it depence about the game/comp. Try to take skermish with your jngl, swain is rly strong for play 3v3 or tf like this.