This question is dependent on the size of your BR. My go to suggestions for BR building through SnG and MTT is to first play the PO freerolls. You can also complete many PO offers and get yourself an extra couple of bucks through PO pts. After that the double or nothing SnGs are always fairly easy. Straightforward tight play will get you in the money on these. They can be a bit tedious, but its a good way to build small BRs. I would stay away from anything that is short stack or super turbo. These games have a higher variance and leave little edge for players.

I have noticed that there are several guaranteed money MTTs that are alternate games. These tournaments have pretty small fields and might be a good choice to boost a BR assuming the buy in is not a large chunk of your BR.