First, try to learn the big crystal orderings for the first 30 levels. Getting to 1m by level 35 is a lofty goal, but it's easily accomplished if you're careful. You get an extra life at 100k, 500k, 1m, and every million after that. Getting them earlier on gives you more lives to work with in the later levels.
Second, when kicking bombs to a lower level, learn to time them so that the bombs blow up while it's still in the air. The reasoning is that it doesn't knock the enemies as far, meaning you can easily manipulate which enemies you can take out by immobilizing an enemy and then going for another on the same level without worrying about killing them.
Third, this also applies with bomb kicking. By timing a kick, you can hit an enemy on a higher floor, either freezing them (normal bombs), killing them (black bombs), or dropping them down a floor (blue bombs). This technique helps out a LOT towards getting the large crystals in the mid levels (40-70), and is indespenable in some of the later levels. Of course, this assumes you don't already have the vertical bomb kick ability.
Finally, be mindful of enemy movements. One thing to realize is that most of the enemies move according to your current position and your proximity to them. Learn to lure enemies to a position that's more beneficial to either beating the level or (preferably) getting the large crystal.
The rest just comes with practice. Took me a few weeks to get to the later levels, then it took me almost a month more to beat the game. The later levels are a serious pain in the ass, and no matter how good you are you will almost always lose numerous lives (such as on level 94 and 96).
Good luck!





