This is a very interesting concept. I have played through most of the MBG levels that don't have gems, and I think this could prove to be something that could have new paths every time. I would love to see some records posted on this thread.
For fun, I'll put up some times of my own to get started.
Edit: Added all MBG Beginner times, and I think I'll just use separate posts from this one when I go to Intermediate, so this doesn't take up so much room on one post.
Marble Blast Gold
Learning to Roll: 2.824 Had an interesting run off the ledge. Could be improved, but not that much.
Collect the Gems: 18.500 Normal ground acts just like ice or space, which will become a problem in many more levels. Also, I found the OOB is surprisingly close to the far side of the interior.
Jump Training: 6.981 Using the wall hit to your advantage can get you up quite high, but you have to have spin to go either up or down. The edge is not high enough.
Learn the Super Jump: 5.911 As expected, sign hit is the way to go. Barely tap it, though, otherwise you will be sent flying.
Platform Training: 5.900 Figured out a little trick to hit the edge of the moving platform softly, just enough to keep me from going down too far. I think this is a very good run and will be a little hard to beat.
Learn the Super Speed: 5.454 I learned very quickly that you shouldn't go over the ramp fully, but rather barely go over it and stay low the whole time.
Elevator: 6.768 The run really depends on how much time you stay on the platform. Too much, and you'll fly OOB. Too low, and you'll have to do a wall-hit to make it the rest of the way.
Air Movement: 8.721 Purely internal clock. It's a race to get off the start platform as soon as possible.
Gyrocopter: 5.309 A little trick to this is to not roll right off the front, but rather more the side. If you go off the front, you will have spare time in the air to float back down, but otherwise, you will be able to go right to the finish.
Time Travel: 5.005 Already said this before, but if anyone with a good internal clock wants to attempt this, I definitely think it's possible.
Super Bounce: 5.261 Exactly same strategy as Gyrocopter.
Gravity Helix: 10.959 Don't hit the big side of the other platform, but rather the sign. If you get a good hit off it, you will be able to continue going in the same general direction while having just enough air to get to the finish.
Shock Absorber: 7.282 Exactly same strategy as Air Movement.
There and Back Again: 31.314 Didn't feel like doing the sign hit on this one, so might as well put it here.
Marble Materials Lab: 12.970 Start your backwards movement when you reach the mud, then get the gem. Make sure you bounce high enough to get to the grass in the air. Don't have too much or too little spin, or you won't be able to brush the gem at the top of the hill. Keep the momentum going as fast as possible to the finish. Yes, I know. Lots of notes.
Bumper Training: 2.823 Exactly same strategy as Learning to Roll.
Breezeway: 5.493 Hit the trim on the left side to get in the air, then go forward as hard as possible and don't turn, for the fan will do that for you.
Mine Field: 2.817 Exactly same strategy as Learning to Roll/Bumper Training. Also, it was weird to see me get gradually better times on the same exact kind of level layout.
Trapdoors!: 3.741 I know what you're thinking: impossible. Just roll and hit one of the trapdoors with diagonal movement. When you reach the next tile, restart the level. Continue as normal, but hit the tiny indent the trapdoor still has left to go up, giving you a small lift. This lift enables you to go faster, since for some reason air movement is much more efficient.
Tornado Bowl: 30.328 This is another one of those levels I didn't really want to try hard on. Also, the tornado is super strong, so actually follow the level's description to beware the tornado.
Pitfalls: 9.394 Hit the little edge/wall that connects the second platform up to the third, and you should get some height. Continue by doing another wall-hit into the big tower structure. With this momentum, you should fly through one of the holes at the top and go to the finish.
Platform Party: 8.327 Same start as Pitfalls, but go back to hit the tower, but not too hard, just enough to get over and to the finish.
Winding Road: 9.283 Again, same start as Pitfalls, but make sure to try to hit the edge for more height. Also, hit the middle tower behind that, and have spin to ensure you have just enough height to make it to the finish.
Grand Finale: 1:09.803 Purely pathfinding. Try to find the best one and don't go too high, otherwise it will slow you down. Also, Yoshi said to use the Gravity Modifiers. Don't. Hit one of the slopes hard enough so you can fly up and hit the gem.
Marble Blast Platinum
Space Station: 13:33.127 Just for fun, but very interesting to get the feel like it is actually a space station. If you want to attempt this, I know this time is easily improvable if you don't have a crappy tightrope section, because icy tightropes are not that fun.
we ball