Incompetech is a good suggestion, I've used them before. I also use another free library which are the Machinima Sound Legacy tracks. On top of that I have a paid subscription license to the monstercat music library. I may also be getting one soon to epidemicsound as I've heard good things about their library, which is also a paid subscription.
If your videos are short you probably wouldn't need a subscription library, but for me with a lot of videos over 10 mins it made sense because it saves me a lot of time and monstercat has album mixes that are like 60 mins+ long that I can just drop into my long videos and they are good to go.