First, get away from the idea of building time. If you want to build time, I suggest the Pilot G-2: you can get several thousand hours from a single pen, and they come 2 or four to a pack. If you value each hour at 150.00, then the pen is easily worth 15,000 to 30,000, and you can get it for a couple of bucks at Walmart. Probably the greatest deal to be found in this century, or the last.
Instead, build experience. But how do I do that, you ask? How do I get experience, and isn't it really hours that counts? No, it's not, and you get experience by making each hour count. Follow me.
Two folks take off for an hour of flight. One rides around the pattern repeatedly, perhaps goes for a lazy stroll about the valley, checks out the dead fall leaves.
The second departs and immediately pulls an engine, and proceeds to do engine-out partial panel work for the next hour, or short field single engine work for the next hour...work that taxes the pilot and makes him her think.
At the end of that hour, one has an hour of logged time, while the other has many times that, worth of experience (but only one hour of logged time). One pilot has built an hour, but the other has gained experience.
When I got hired for my first multi engine job, I had fifteen hours total time in multi engine airplanes. A friend, employed at the same location, bought into a twin, and "built" hours. He got a Twin Bonanza, and flew it until he was in debt to his eyeballs and beyond. We interviewed at the same place, and were both offered a job. He had no advantage with his built-up time; we were judged by an interview, and a sim check. We both passed, we were both hired.
You cannot be hired without the proper basic credentials. That much is certain. You're showing 900 hours on your screen bio, indicating that you still have a way to go. Don't get impatient. 900 hours is just starting out. You can't even make the basic 135 IFR minimums yet, so be still, and concentrate on the fact that in a time when many are out of work, you are being paid to fly. That is no small thing.
You'll need to get your multi engine land rating when able; you have to have it. You have time, however. You can always hire on with a firm flying singles, and progress to the multi equipmet as opportunities may arise. Bide your time, be patient, and opportunities will arise. So long as you remember that you're just starting out, and have a great distance yet to go, the stress of thinking you have to be somewhere right now won't bother you. Don't let it. You don't need to be anywhere but where you are. Live within your means, don't mortgage your soul, and be happy that you've got a flying job. Get your training when you can, and when an opportunity arises to fly for a firm that utilizes both singles and multi's, then do so.
Good luck!
In any event, I was patient and eventually got into the multis at Riddle. At that point, I had multi students coming out of my ears! 
