OP: What do you currently have and what, if any, of it do you think you need to replace?
Lightweight, quality kit costs money – unfortunate but that’s the way it is. The big items (tent, sleeping bag, sleeping mat, rucksack) will be the items you can save most weight/bulk on but will cost most to do so.
Alpkit are worth looking at for bikepacking kit, I’ve not used their camping kit so can’t comment on that. I’d avoid bikepacking with a big rucksack if you can, the weight is too high and makes things too unstable. To begin with you can just strap dry bags to the bike rather than going the full hogg and getting harnesses/bags etc.