Try to quarantine as best you can. I completely understand not having a lot of space to work with. I have to have my snakes confined in my bedroom...so when I get a new addition, the farthest place away from my collection is in my closet. I just make sure my closet has a bottle of germ-x, feeding tongs for that room, and it's own scale. I never handle the snake in quarantine on the same day as the rest of my collection. I just try to put as much space between my snakes as possible. I recently got a big 2000g girl from the breeder I got my male from. She's still in quarantine even though I know the breeder has a great facility and very healthy animals.
Just try your best.