Donvalve

Normals
5A - Fast and far range. Good short range poke, although you don't get anything for it.
2A - Lightning fast jab. Good for beating other people's stuff.

5B - Good poke, moves you forward. Slight frame advantage.
2B - Great low hit. Knocks down, but techable. Watch for the tech and go for resets in the corner. Good for mixups. Hard (or impossible) to punish on block.
6B - Overhead dropkick. Throw invincible of course, good to setup mixups or fake hit setup into throw.

c.C or 4C - Same move, two ways to get it. Vertical attack. Strong and fairly fast, so used in some combos and maybe as AA?
f.C - Very nice poke. Huge range, fairly fast.
2C - Very good low poke, similar use as f.C but a low hit instead. Huge damage.

2D - Rolling overhead. Large range, but somewhat slow and very unsafe on block.
6D - Sketchy Anti-Air. Gets juggles for solid damage near the corner. Has a decent hitbox but a lot of recovery.

j.B - Crossup. Small hitbox, can be used to bait parry with a wiff.
j.D - Crossup. Much bigger and stronger than j.B.

Normal Throw - Very short range, low damage, and slow in comparison to his command grabs. However, it has less recovery on wiff and is easier to input.
Chains
2A 2A ...
2A 5D
2A 6B
5A 4C
5B 2B
Specials
360A/C - Don Swing
Command Grab. Has no startup and can be used as a reversal. Use it for what you'd used a high damage command throw for. Mixups, punishes, reversal, anything.
A version has much larger range but does less damage.
C version range is very short, but still longer than his normal throw.
41236B - Catapult Hammer
Dashing hammer attack, can be delayed by holding B. Hits a huge area so can be useful to hit people who instinctively try to jump out of throws.
Has Super armor after a brief period of vulnerable startup, which ends when the hammer beings to swing (or the button is released). Has no invincibility to throws.
┕▶ P - Catapult Hammer Break
Cancels the dash without swinging. There is a minimum distance you have to cover before you can cancel it, so you may need to hold B to prevent swinging if you wish to cancel it. Useful for covering distance after a throw or knockdown.
41236D - Catapult Throw
Dashing throw. Same general properties as Catapult Hammer. However, vulnerable activation time is extremely short and basically impossible to hit out of reliably. So as a general rule, this will beat mashing attempts.
214K - Hip de Don
Butt slam. Hits the whole screen, can be blocked or Gatchied low. Good to get knockdowns from full screen to help you get in.

Supers

236236K - Flying Don Pancake
Anti-Air grab. Can be Gatchied, but must be done before the super flash. Solid damage, generally very good for AA or combos.
720P - Don Don Swing
Super Command Grab. Rotate the joystick rapidly to increase the damage it deals! Can't be jumped out of after the super flash. Like his normal command grabs, it has no startup and makes a good reversal. Great for mixups in general.
Heat Up
Speed Up!!
During Heat Up, Donvalve's forward walk speed is greatly increased. In addition, as long as he is walking forward, he has infinite hits of armor, even to supers! He will still take half damage from all hits though, and he is still vulnerable to throws.
This can be used as a Reversal if timed correctly.

Enhanced Specials

6C - Goldon Swing
A new command grab. Has some extremely small startup (which is possible but extremely unlikely to hit him during).
Does damage similar to his 360C but only has the recovery animation of his normal throw.

Enhanced Combo Potential

Like all characters, Donvalve's combo potential increases while in Heat Up. This gives him the ability to combo off his 360C in the corner, and his Catapult Throw anywhere. If this is useful or not is questionable, but it's there.
Kara-Cancel
Normally, Donvalve can't cancel into his Hip de Don special. It's possible to do this by using a Kara-Cancel however. Unlike Urs, the method is actually very easy. The usefulness of it however, is questionable.

One method is to Kara-Cancel 2A into 5D:
2A 5D-Kara Canceled into 214K
The easy method of inputting this is to just do:
2A 214D~B

Likewise you can do the same thing with 5A into 4C:
5A 214C~B

And similar can be done with canceling 5A into the Catapult moves:
5A 4C-Kara Canceled into 41236K
Combos

Basics

5B 2B

AA 4C 236236K

(Near Corner)
AA 6D, 2C
(Best Damage)
(Near Corner)
6D, 4C
(Will work at any height)
(Near Corner)
6D, 236236K
(Super version)
(Near Corner)
6D, 2A 6B (wiff)
(Throw Setup)

(Mid)
AA 6D, f.C (41236B~P)
(Situational, but useful)

Gatchi Counter

(0 far)
GC 2C
[715]
(0 close)
GC 360A/C
[625/909]
(0 very close)
GC 5D 41236B
[1098]
Fairly finicky combo, but the most damage you can get.
Generally, if you GC it's best to just use the first combo if you are far, or the last combo if you are close.
(1 close)
GC 720C
[1449]
(1 anti-air)
AA GC 4C 236236K
[1535]

High Gatchi Drive

(1 any)
j.D |> 6, 2C 236236K
[1431]
(1 mid)
6D, 4C 236236K
[1440]
Much harder for only a little damage, and doesn't work near the corner.
(2 corner)
Heat Up, j.D |> 6D, 4C, 6B, 2C 236236K
[1975]

(1 corner)
Heat Up, j.D |> 2C 41236B, 2A 4C 41236B
[~1438]
(2 corner)
Heat Up, j.D |> 2C 41236B, 2A 4C, 236236K
[~2015]
Only works on Cedric, Freed, and Ashley. Possible but very hard on Donvalve.

Low Gatchi Drive

(0 mid)
Superjump, 360C
[801]
(1 mid)
Superjump, j.D |> (5A) 5B 2B 236236K
[1492]
For the corner, replace the Superjump with a regular jump. Or for the 360C, don't bother jumping at all.

Heat Up

5A 4C

(corner)
6D, 5D 236236K
Can also skip the super and use it as a reset.
(corner)
360C, 2C
(corner)
360C, 236236K
(deep corner)
360C, 5D 236236K

(corner)
360C, 6D, 2C
(corner)
360C, 6D, 236236K
Only works on characters who are at least a Little Floaty (as per this page). Doesn't work on Face.
41236D, 2A 6B (wiff)
(Throw reset)
41236D, 2A 236236K
41236D, 2A, 236236K
For the last one, you can reset instead of directly comboing the Pancake. It gets you ~300 extra damage and will be difficult to Gatchi, so worth a try.