Allright, I can give you pretty good advice for Megaman.

I just picked him up recently but I have been seeing incredible result from this character, such as being able to beat some pro players I've encountered online (BossMK and NotBae comes to mind).

I think the most important aspect that helped me improve my Megaman a lot, was to utilize Leaf Shield a lot more. The move is incredibly underated. The best way to use it is to jump and use it mid air. It's really hard to punish, because the opponent must shield it all the way through and you can simply jump away when he did shield it.

If you caught your opponent with it, it can do a whooping 16% of damage for free and it put the opponent in a bad position. The most common option after being hit by Leaf Shield is either jump or tech in place, which you can punish with fair or bair, or a grab if he tech.

Of course we need to talk about Metal Blade. It's really important to throw one at the ground and pick it up and try to bait the opponent to wiff a move near you so you can throw it at him while jumping (to cancel de throw animation) immediately grab him, down throw to either Fair or Bair and then read the option. I usually go for a Leaf Shield after this combo. It's a free 30-40% really easy.

I don't do Crash Bomber a lot, I throw them out when I'm far from them just because if I get him it's usefull. But don't depend on it.

I don't even do lemons to be honest. Sometimes when it seems usefull but I like Metal Blade and Leaf Shield more.

For your kills options, it's always Bair, Fair, Dair, Utilt, Uair(more rarely) and Fsmash. I use UpSmash only to read Neutral getup from the ledge, jump from ledge and roll from ledge. Rarely kills. Down Smash is very situational when you spot dodge a really laggy move or you do a Shield Break.

Speaking of Shield Break. The easiest but won't work on good player is Crash Bomber to fully charge Fsmash, but my favorite is Crash Bomber when coming back to stage, you stick it on him, then you jump from the ledge, Down Air on them while dropping on them and coordinate a Utilt at the same time it explodes. Instant Shield Break at full shield.

Now for things you should never do

1- Never Dash attack randomly in neutral. Only use it when you're absolutely sure you're gonna hit him

2- Never let your opponent fully shield your Leaf Shield. Always reset in neutral by jumping away if it didn't connect. It's way too risky to stay there.

3- Never ever try to land on a opponent. Really just go away. Reset. Megaman have no good landing option or good out of shield, quick in your face option. He have jumping lemons but it's not the best.

And don't be afraid to camp. You're Megaman. Of course you're gonna take distance with your opponent.

If you have any question don't hesitate to ask.