Thanks to the buffs Ruby received in the version 1.5 update, Ruby has a very practical and effective oki game that revolves around the use of Gun Blast to create safe-jump set-ups at the end of essentially any combo. Exactly what sequence of Gun Blasts that should be used for oki depends on the opponent's position (how high they are and how close they are to the corner) and what move Ruby used prior to the Gun Blast. Her Petal Burst super can also provide safe-jump oki if the opponent is launched into the corner but this requires meter and combo routes that can end with supers.
1) Sweep (2C): Works anywhere on the screen. Only grants safe-jump oki if sweep connects against airborne opponents.
2) Gun Blast (214A): Works anywhere on the screen. Grants safe-jump oki depending on the chain of Gun Blasts used.
3) Buzzsaw Blast (j.236B): Air only. Works anywhere on the screen, but is more effective in the corner.
4) Corkscrew Slice (A+D): Ground only. Works anywhere on the screen. Has minimum damage.
5) Petal Burst (236B+C): Ground only. Only works in the corner. Has minimum damage and sets up a safe-jump but costs two bars.
Choosing an Oki Route
1) Sweep is a very simple but effective oki tool. It isn't jump cancelable like many other sweeps but it can still lead into safe-jump oki by hitting an airborne opponent with this move (even the slight bounce from a 5AAA hitting airborne opponents is enough), a jump into an IAD can be buffered, resulting in said safe-jump. In any other case, like a raw sweep, Ruby only gets basic meaty oki.
2) Gun Blast is Ruby's main oki tool as it can be used at the end of essentially any combo and provide safe-jump oki at any time as long as the combo timer hasn't been completely emptied. Only the A and B version can generate proper oki on hit as the C version either ground-bounces or launches the opponent up and away which will allow the opponent to air tech if it is done late into a combo. While only landing a single Gun Blast is needed to generate a knockdown, additional Gun Blasts can be used to alter Ruby's position for better oki. Mid-screen, this sequence is normally 214A~B~C, which leaves Ruby airborne above the opponent and allowing her to use j.A as a safe-jump meaty.
3) Buzzsaw Blast is the attack Ruby uses to end essentially every combo. However, this attack has very poor oki on its own, launching opponents all the way to the other side of the screen, thus making it only effective in the corner. Its ability to be canceled into Gun Blast makes this move essentially obsolete. Still, it is very easy to use and still provides meaty oki in the corner.
4) Corkscrew Slice has the highest damage of all of Ruby's meterless attacks. However, it has the worst oki among all her options as it only grants a meaty 5A in the corner due to its poor frame advantage. In some situations, like hitting a this attacks max height, the frame advantage improves enough to even grant a safe-jump, though this is highly impractical and almost impossible to do mid-combo even with an assist. Only use this in the corner or when damage is more important than oki.
5) Petal Burst is Ruby's strongest super both in terms of damage and oki. It provides safe-jump oki so long as the opponent is cornered by this attack which is quite likely to happen due to the attack's immense corner carry. It also works if the Duo Distortion Skill version is used, making useful for getting safe-jump even if the partner struggles to do so on their own. Should be used to end corner combos whenever possible, though note that this move costs two bars and incurs a 180 frame metergain cool-down so don't use this carelessly.