If you want suggestions i highly recommend super mario maker, thats my eternal favorite concerning mario games. Yeah, i know the amount of junk online is kinda heavy, but let's put that aside here and say there's no right or wrong way to make levels: you decide how to make them.
Sure, we have a big list of 'don't do this, do this instead' because we want a fair challenge without the level being based on luck (what ive called the guessing game in some cases) or so insanely difficult it just takes the fun out of it, but in the end it really falls on the user to decide how and how not to make a level. There's an endless supply of levels to make and its an excellent way to pass the time if you're bored with nothing important to work on in my opinion.
There's just so many ways to enjoy this game its hard not to love in my opinion ! I apologize for getting off topic though, just made a suggestion to you >~<