When should I play with low cards?
Pretty wide question, nothing is ever that black and white in poker
So many things matter: position, stack size, table size, what has happened before your turn, your own mindset etc.
I play 6-max cash games and I usually play (open/flat call) low suited connectors preflop, no matter what position, if I am able to see the flop by only paying 3bb, maybe 4bb at maximum. Not every time though and that is hard to explain. Sometimes I even call bigger raises, even when someone 3bets. You just have to play to gain experience and then you start to pick up good spots to play them. The gap matters as well: I'd much rather play 65s than 63s. Actually, I almost never play that 63s cause that is already close to rubbish. Then again, I play 65s almost every time if nothing weird happens preflop.
The big picture here might be that I play them when the gap is only one card at maximum. And they got to be suited. But then again, if your position is good and you get to see something like 54o cheap, then why not. Your goal is to get lucky with them and hit a straight, two pairs or something like that. Your opponents don't know what hit them if you do get lucky. Like I said, this is really hard to explain cause so many things matter. Maybe you should just start to experiment with them and find a way that works for you. The good thing about low cards is that they are easy to throw away if nothing good comes from the flop. Just remember to keep a nice balance of what you play and what you don't.