Notice the groups of 5 coins floating in space? You must get these. Jump into them and then spin to boost yourself back onto solid ground before you fall. Despite being in the open, they're actually pretty easy to get once you practice. Without these, my route below won't work. Don't worry if you can't get all 5 every time, try to get most of them.
Leave yourself a path back to the start point because that's where the star appears--but you probably already figured that out from the Mario meets Mario challenge you've already done in the toy galaxy.
When running across the spinning platforms, run along the side the starts to spin up (the side closest to you as you stand at the start). This avoids needing to jump at each square.
Never stay on the spinning platforms for more than a moment. For some reason, Mario has a bad habit of not jumping well when the slope gets too steep. I never try to go back to a spinning platform I've already triggered, even if I missed a coin.
Ignore the clock. It won't matter.
Finally, my path, as best as I can describe it.
Head left and long jump to the yellow spinning platforms. Collect some coins and turn right.
Long jump over the small gap (2 squares, I think) with the liquid that kills you and then immediately turn around and jump back, collecting the other coins on each pass over the gap.
After you jump back, Mario makes a sharp right turn (should be left based on the camera's perspective) and jumps over to the first row of what I'll call the zig-zag section. I call is zig-zag because after making this jump, I'll go left and right one row at a time collecting all the coins on each row. I do this until the last row of yellow spinning platforms before the area where you see the 1-up mushroom.
Leave yourself some green disappearing platforms for later and cut diagonally across to the area with the 1-up mushroom. Collect all coins here (the 1-up is optional, and usually messes me up, so I skip it).
After collecting those coins, meander your way to the opposite side of the board, collecting as many coins as you can before you long jump across the gap. There's one coin per square here, so collect them all before making a sharp turn and making the most difficult long jump of the level. (Collect the coins on the edge of the board first so you'll be able to make the long jump.)
You'll need to do a double long jump to cross these two gaps. Make sure your aim is true so you can collect all these coins. If I make it this far, which isn't often, I usually have about 97 coins.
Collect the final few coins you'll need after long jumping back near the starting platform. You should have left these alone at the start of the level to give yourself the ability to get back to start and collect the star.
Good luck.