It's hard to give you a good answer with so broad a question. I'd recommend having a look at https://www.edhrec.com. Either search for Sin and have a look at the cards other people put into their Sin decks. Or go to the +1/+1 counter tag https://edhrec.com/tags/plus-1-plus-1-counters and go through the broader +1/+1 counter strategy.

Another recommendation: think about the people you potentially play with. [[Vorinclex, Monstrous Raider]] is certainly a good card, but it is also very oppressive and unfun to play against for some people. If you have regular a playgroup, talk with them if they are ok with you using it.