[E] Dizzy's plasma blasts can be dodged by enemy players, since it's a projectile and does not instantly effect enemy players.
[E] Dizzy is great not just for blinding enemy players, but also for gathering information. You can tell how many enemies it's seen by listening to the number of times it shoots it's plasma blasts.
[C] Mosh Pit looks like a molly, but isn't like a regular molly. It does one large chunk of damage to anyone in it's radius, and can be used to clear out key points on the map when taking or retaking Sites.
Unlike all of Gekko's other abilities, [X] Thrash can only be picked up and reused once. This can allow you to use it early in the round to take space aggressively with your team, and then you have another use for it later in the round as well if your team is able to successfully take and control that space.
[Q] Wingman can be destroyed by taking taking from weapons and utility. So, try to create opportunities for Wingman to safely plant the Spike, and take advantage of the fact that you don't have to plant the spike to make it even easier for him.