Beat all the Staff Ghosts in Time Attack
To defeat all the ghosts will be no easy task. Here is all I can do for you, the rest will be up to pure over the top skill. Firstly you will want to be Sonic. He is built perfect for most of these stages and as is the Sumo ghost. With Sonic you won't be at a disadvantage. To do this you want to abuse drift boost as much as possible (especially on plane sections they will never keep up) and you will want to find a shortcut that cuts time off or gives you a real good speed boost. Some secret shortcuts will actually slow you down or take longer! This gives you an edge over expert Sonic. Easy medium and hard ghosts can be beat on lap one. But expert will take what feels like forever. But on some maps they are extremely easy to beat. It will get easier with time as you will become better and better.
Two absolutely huge tips I can give you: Save the boost for an entire lap and drift to a level 1-3 boost whatever is possible just before the finish line. Unleash the boost and use the item boost, too. This will immediately give you a huge advantage against expert ghost straight away and can give you that precious 1-2 seconds that will beat him.
Secondly there seems to be a glitch for a lot of people (but not everybody!) where if you can beat the Sunshine Tour Mirror ghost with Sonic and his Standard Mod it's possible to unlock Yokozuna and soon after possibly even the triple star license! It's unknown what triggers it exactly as the amount of ghosts and stages beat vary for every person. From unlocking it and a mere 35 ghosts all the way to getting it at 150 ghosts, there's no way to find out unless you give it a shot. Doesn't hurt to try eh?