Combo s101:
First of all, you don't need to do true combos to do well in The Moon Fields. Attacks can stun opponents for a period of time, and a string of attacks that keeps the opponent stunned is called a Combo. But because there is no universal "don't get hit" button, strings of attacks that almost combo can be just as good. The few frames you let up may let your opponent wriggle out of your grasp, but that's OK because unless you miss (which you should never do), you will probably keep your advantage! Obviously letting your opponent control their opponent for 0 Frames is best, but they might not be able to stop your assault if you give them just 1 or 2 or even 5 frames of breathing room.
In general, there are a few attacks that will combo into themselves. The Crossbow's stun is long enough that you can reload and fire off another bolt before your opponent recovers. The Starlight's Forward Stepback Thrust stuns for 30 frames, but only takes 26 frames to enact --- that gives you 4/60 frames of leeway to repeat the attack and score another hit! But these two (and most of the others) come with a high barrier of execution. Hitting an enemy with a Crossbow bolt will stun them, they will slide forward with whatever momentum they had, and the bolt will push them back --- that means, unless your enemy is walking straight towards you (or not moving at all!) to score hits with consecutive Crossbow bolts on a moving enemy is incredibly difficult.
Some attacks that do not combo into themselves may combo into other attacks. Attacks have Startup, Active, and Recovery frames. If an attack's Start Up is long and the Active portion is towards the end of the animation, then it is likely that attack can combo into an attack whose Start Up is quick and the Active portion is towards the beginning of the animation. The Broadsword Neutral Backhand Swing deals damage towards the end of its attack, so it combos fairly well into The Broadsword Tilt Forehand Swing. One of the tricky things about fighting in these 3D spaces, though, is depending on your character's orientation you may deal damage early during active frames or you may deal damage late. Orienting your characters correctly to key to these types of combos.
The last thing you will look for to up your combo game is utilizing Dash/Jump Cancels for offense. The Dash/Jump cancel is a technique for players to quickly get out of a successful attack by either Dashing horizontally or Jumping vertically. After this movement is started, the player can continue their evasion or get right back into the attack. Some of these combos are easier than others, and some are incredibly difficult! Most of these combos can loop into themselves or other combos, but they become unwieldy and difficult to maintain after a couple hits. One of the easiest of these combos is Knights' Sword Forward Stab > Dash Cancel > Knights' Sword Forward Stab and repeat. When creating these combos, consider the Analog Stick's position for the attack, the type of movement you want to chain, and the attack you want to use to follow up. Going from a Forward Attack to a Jump to a Forward Air Attack is doable, but it can be very difficult.