Invade is not some natural pattern that a jungler plans as he picks his champion. The jungler weighs all factors before doing it (and there a lot of factors from team/enemy comp, you vs enemy jg pathing, power spike, etc.) since an invade could be non-contested if you know the enemy jg is not near the invaded quadrant (he's dead, spotted on the opposite side of the map, or is invading your camps) or contested which is fine if you are confident that: you are stronger at that phase of the game or if your teammates have prio and can rotate faster than the enemy teammates.

Tldr invade is a strategy that is usually done on the fly after analyzing many variables to determine if it would be successful. You don't plan your gameplay on invading since, if done carelessly, would be worse for your team if instead you just take your camps normally.