Overcoming slow reaction time

[AirSupremacy]

The beginner guide for Guilty Gear AC seems very advance to me. It may be because my last fighting game was Street Fighter II Turbo on the Super Nintendo. I don't have a particular style. For the Street Fighter game, I basically beat the hardest setting by spamming Ryu's fireballs and neutral jump roundhouse kick as my anti-air. I think my biggest problem in Guilty Gear is the speed required to execute some of the moves such as guiding Millia's Secret Garden or force Roman Cancels. Also lacking is the ability to react to the moves of my opponent and make adjustments on the fly. To me it all is flowing instantly whereas most players could pick out from the animation what's going on. I'm willing to practice hard and long because I just love watching fighting games. However, without a way or method to go about solving my glaring weaknesses, I'm afraid I'll be stuck in the spamming fireball stage forever.

[destruction_adv]

Don't worry about it, reaction time will come as you get used to the game. Everyone was at the spamming fireball stage at one point, but with prractice you pull yourself up. Also, the more you like a game, the easier it should be to practice, and since I've yet to play a more likeable game than GG (In my opinoin), trust me when I say practice rarely seems like work in this game.

[Hellmonkey]

You should spend some time in training mode getting down your combos and getting a good feel for all of the character's options.
Once you can naturally do any of your character's attacks at will, it will make the decision making process much quicker- this is what is likely slowing you down, not your physical reaction speed.

Before working on something like reaction time, work your character knowledge, game knowledge, and execution.
Reaction time will come naturally when you have an idea of how to move and attack.

[Rainbow Mash]

Getting a grasp of the meta-game definitely helps, reactionary anticipation is far faster than raw reaction speed.

Being able to read your opponent is a necessary skill to have anyways.

[TD]

theres also some things you can do before practicing to have optimal brain function. stretch, breathe deeply, etc... so you spend more time learning and less time yawning