Plenty of people use blankets - I can't remember the exact advice but essentially have the blankets tucked in well around the foot of the mattress to prevent your baby from pulling them up or wriggling under. If you fold the blanket so that it doubles up then it counts as two blankets.
It's up to you and how your baby is, but personally I only ever use sleeping bags. DS just wriggles so very much, turns onto his tummy during sleep, turns back again, lies horizontal, as well as liking to pull on various things... a blanket simply wouldn't stay put and I know I'd be every-so-slightly paranoid that he'd cover his face with it. Quilts are the same plus extra possibility for overheating.
As for bumpers they're definitely not necessary. They're a suffocation risk also. Most children are fine, but if your baby is very active and regularly bumps or gets a hand or foot stuck between the bars you can buy safer alternative products, such as an Airwrap. It's essentially a lightly padded mesh thing, it's similar to a bumper but a child can breathe through it.
*I'd like to add that this is all from memory when I first looked into this a year ago when pg with DS, my apologies if it's not 100% up to date but we decided to bypass all of this and just use a travel cot! It has mesh sides so no bumping or suffocation risks, nothing to climb on to get out, and it's quite roomy. He will be in there until he's ready for a toddler bed. Plus it's light and will collapse away when we're done 