3 clutches would give you a good shot if they are decent sized clutches but you never know how long it will take you to get those three clutches. Putting all of your hopes into one female is a tough way to go. There are just so many things that can slow you down. That female could be a poor feeder, slow grower, slug layer, small clutch producer, every other year breeder.... If at all possible I would try to at least pick up maybe 2 spider females as well (unless you can afford more bumblebee's). That way when they are up to size you could breed a pastel lesser to all 3 of them and have a decent shot at a queenbee in your first year.
Just as an example, I paid a ton of money for a pair of Het lavenders back in 05. That female just produced her first good clutch for me last season. I actually produced lavenders from raising up and proving out my male het lavs possible het offspring (bred him to some normals in 07) before I got my first good clutch from the original 100% het female. To top it off that original het female is looking like she is only going to be an every other year breeder.