free roll players are terrible. will literally stack off with anything, cannot maintain there stack, will spew, will tilt, won't 3 bet, won't shove into short stack, don't have a clue about the bubble. need i go on haha. basically if you play a solid, tight game you will get a lot of chips.
at mtt's where there is a buy in, usually at the lowest ones you still get a lot of free roll type players. however there are usually some okay players who have an idea of what they are doing. as you move up in stakes there are still exploitable fish but they are better and not as spewy, but still a great source of chip building. gl!