30-60 flopped a set best line?

[worm33]

Typical crew at canterbury, great game been runnin kinda cold not many cards been seated about 2 hours. I am dealt 55 in my bb. 3 limpers a raise from a VERY weak tight player prolly meaning aa or kk. 1 cold caller sb calls I call. 7 to the flop. Flop comes 5-8-9 with a flush draw. Honestly I dont know if the Pre-flop raiser will bet here since he likes to slowplay big hands, or what he thinks are big hands. Whats my best line after the sb checks? I think I played it very interestingly, i'd like to see what u guys think.