5s is mostly dominated by a more competitive players than the 2v2 and 3v3, in my experience anyway.
The 2s and 3s brackets contain the most class imbalances and thus is easier to rank gimmick teams to 2k rating, however the 5s bracket are more balanced and tend to keep players who are actually interested in the competition. Usually...

best bet is to keep playing and get the gear and practice for when season 4 comes out where everyone starts at 1500 again.