Something that worked with my gelding was trying not to pull back, and then planting my seat down and squeezing my legs as hard as I could. Until my horse adjusted to me, I wouldn’t loosen up with my seat and leg. I did this every time he got not-collected (?) for a couple of rides and eventually I could collect him completely by just slowly tightening my leg. Don’t get frustrated with your horse, don’t kick if they slow down but gently don’t let them stop.
Everyone says comes from the hind and I know that but I've always been taught to get the horse on the bit in order for collection. How do I do this without a bitted horse even if it has nothing to do with that.
collection comes from the hind
Have a look at dressage training pyramid. There a few things you need to work on before you'll be able to collect the horse and develop lightness in the forehand