Or you could go just straight Beautifly belted. But as aforementioned its Luxchomp thats your weakness, unless you can get Metapod set up early. But then Bright look will just toy with you until you have nothing left.
Tangrowth COL, AR, SF are the best Tankers right now in the grass column. Choose one.
But if Luxchomp isnt in your meta, then Beautifly may be a good option. But dont pair it with Tangrowth. Both are Energy siphons, and it takes too much time to set up both. Just go with one or the other with a Shaymin X tech (until rotation, then Serperior from B/W).