Using pomegranate tier GMS names:
Builds for both Alpha and Beta, with a very specific order because you learn skills every 5~10 levels. These are designed for optimal training in Mirror World Dungeons, and then whatever it is you do at 180+.
At 100, you get 3 skill points from a tutorial and upon finishing a quest, you get +1 Piercing Thrust, and +1 Shadow Strike. Put the three points you get into Long Sword Mastery and Moon Strike. Combination 1's attacks are left at level 1 as they're only used if you accidentally miss with Combination 2 and 3, and need to reduce some cooldowns. You only need to use Moon Strike -> Piercing Thrust to enable Flash Assault again, though level 1 Shadow Strike is fairly strong at this level.
Save up points and max Flash Assault first. Combat Recovery is rather useless. A single point for the +11% Recovery should be enough. Until you learn Combination 3, you shouldn't be able to spend Time Force faster than you earn it, but by the time you actually learn those, you can start to use Assist effectively to deal damage and recover Time Force.
Spin Cutter, Rolling Cross, Rolling Assault, and Reinforce Body are all important to be maxed first as they are primary training skills, all part of one effective combo, Flash Assault -> Spin Cutter -> Rolling Cross -> Rolling Assault. If you oneshot monsters with Flash Assault, you can delay getting Spin Cutter since if you don't have it, Flash Assault can lower its own cooldown to 1 second. You lose some damage utility against the boss, but Beta should suffice. Reinforce Body just adds to Alpha's ridiculous critical rate. Wind Cutter is important to max as it deals an insane amount of damage to stacked monsters, and it can easily clear a large area in a single use, especially if you Rolling Assault a group onto a boss.
Wind Striker is rather useless, and is only really used to Assist and chain to Storm Break later, so it's left at 1 for now. You could even consider leaving Wind Striker at 0 for now so you don't accidentally push away your Vortexes.
Advanced Spin Cutter, Grand Rolling Cross, and Advanced Rolling Assault creates your best combo. These can each OHKO monsters in your level range quite easily if you have some amount of funding, such as just gear, or character cards, Link Skills etc. They by far do the most burst damage of any Alpha attacks. On the other hand, Storm Break can be useful for the range, but it's more useful for the Assist and learning Advanced Storm Break later.
Critical Leer gives a huge bonus in damage and survivability since Alpha has such a high Critical Hit Rate and attack speed.
Maxed Advanced Storm Break would be nice to have immediately at 180, but the other Advanced outshine it quite heavily. It's fantastic though for doing things like clearing ToT and any long flat maps with its Vortex and Electric Field. Every other skill can be maxed now. I would recommend Wind Striker first for a stronger Combination 4 chain, and then Combat Recovery unless you use Combination 1 as a standing attack at bosses.
At 100, you get 3 skill points from a tutorial and upon finishing a quest, you get +2 Air Raid. Put the three points you get into Heavy Sword Mastery and Rising Slash. There are enough points for Beta to max Combination 1 rather early. Flash Cut is pretty good for damage. It's decently fast and has long range. Max it and then save up the rest to max Solid Body immediately.
Due to the way Combinations work, if you don't know Throwing Weapon, Flash Cut will activate Rapid Time and reduce its own cooldown to 1s. I would recommend not learning Throwing Weapon as it is not that useful. It requires jumping to reach its full range, meaning you can't actually use the chain delay. It also requires precise aim for it to hit monsters twice, and it doesn't benefit from Heavy Sword Mastery's Total Damage as it is a summon. As such it has a low base damage of 450%x2 at max level. It also does not activate Rapid Time because it is a summon. Instead, you can play with 1s Cooldown Flash Cut.
I recommend maxing Rising Slash next as it would first balance the damage so you can Rising Slash one group, and then Air Raid the next, rather than your Rising Slash being too weak, and your Air Raid being too strong. Also, you can use Rising Slash to reduce the cooldown of Flash Cut, and then follow up with a Flash Cut instead of a Air Raid instead of waiting that extra second, i.e. at a boss where you don't have to travel.
Learning 1 Spin Driver provides a somewhat useful effect. It's not particularly that strong, but the pull can be good and it's an AOE around you, something you'll be lacking up until now. Unlike Flash Cut, it is best used for Wheel Wind at 125 or Assisting with Rolling Cross at 120. Wheel Wind is fairly strong at this point, so save up points to max it immediately. It does become a lot less useful later on and detrimental to DPS though, but it has good utility and damage for now.
A single point in Armor Break can be useful now with Wheel Wind activating it often on anything that can survive long (I would assume Critias Dungeon at this level, possibly a Dungeon Boss). Things don't really have high Defense though to justify more points this early, especially when they die in under 4 hits. At this point, everything is maxed as you learn it.
Combination 4 has really tall range and can easily OHKO things. Air Riot is really strong as well with its Shockwave. It can be difficult to aim because of where it appears though. At 155, max Throwing Weapon to unlock and max Advanced Throwing Weapon. Advanced Throwing Weapon is likely to be your primary damage dealer as Beta. You can use it to clear monsters by casting it and moving forward if you're strong enough, and its damage is extremely high at bosses.
At 165, 1 point in Advanced Wheel Wind for the utility pull would be best. It allows you to pull in things from a very far range, and if you Assist correctly, Advanced Rolling Assault will kill them. Advanced Wheel Wind itself isn't that strong or useful for damage so it's left at 1. Immune Barrier gives Beta the survivability that she lacks compared to Alpha's Divine Leer. It's still worse, but effective. I believe around now you can start trying Critias Dungeon Hard Mode, and if not, at 170 with maxed Advanced Earth Break and Advanced Rolling Assault you'll be strong enough.
There are enough points now to start on Armor Split, up to 16. The benefit of more is for higher activation rate and duration, but the most important is stacks first. Advanced Wheel Wind should be able to stack it to max really fast, so you don't have to worry about activation rate, and constant attacking should keep up its duration. 11 Spin Driver leaves you with enough to max Critical Bind immediately at 185 so you can have more utility at bosses. Now you can max Spin Driver for higher damage when you're lowering your Advanced Throwing Weapon cooldown, and then Armor Split for the extra effectiveness. Advanced Wheel Wind comes last as it isn't really used for anything.
BASED KOREAN NAMES