League of Legends (LoL) Question: STRONG LANE IN 3V3 - SUMMONERS RIFT

A good comp in 3v3s is subject to variation. Obviously you and your teammates will want to play to each of your strengths. For example, a pusher/bruiser champion like Olaf, a high CC tank like Zac, Maokai or Nautilus, and a burst mage like Veigar or an assassin like Talon is a very strong team, but if you're an ADC main on Rift and don't have much experience in those kinds of champions, then playing an ADC could be done in place of the mage/assassin. Snowbally champs like Riven and Yasuo also do well in this mode, and wombo combo compositions are quite strong as well. For example, a Malphite top lane, Yasuo bottom lane, and a Wukong jungle can work quite well.

You can always just go with champions you know well, but if you want specific suggestions I'd check out the tier lists over at theshadowisles.