One of the best grass types out there in my opinion is gourgeist. It's available pre 4th gym I think? With it's HP it can take hits, learns trick or treat (which really helps out) and hits hard. It may have a problem with powerful special attackers and is fairly slow, but run it with trick or treat/seed bomb/shadow sneak/leech seed or will o wisp, it can be a very good bulky attacker for your team.