For example, I want a fireball to circle around my sprite while its also moving

I'll show two options…

1. Motion blocks

point in direction (90)
forever
turn cw (10) degrees // make the sprite constantly rotate
go to [player v] // go to the center of the circle
move (50) steps // move away from the center by the circle radius
end

2. Trigonometry

set [angle v] to [0]
forever
change [angle v] by (10)
go to x: (([x position v] of [player v]) + (([cos v] of (angle)::operators) * (50))) y: (([y position v] of [player v]) + (([sin v] of (angle)::operators) * (50)))
end

This one is a bit too long for the page, here it is again with variables:

go to x: ((player x) + (([cos v] of (angle)::operators) * (50))) y: ((player y) + (([sin v] of (angle)::operators) * (50)))

Swap the sin and cos if you want the angles to be the same as Scratch's directions.

Thanks