That was a pretty good match. A few things:
1) Dair is great, but do NOT use it as a reaction to being knocked into the air, because even if you hit with it, its landing lag is horrible, and it always sends people straight down, so unless they get spiked offstage, they'll be in a perfect position to answer with a getup attack. A much better option if you see people chasing into the air is to use Wizard's Foot, as it spikes people away from your landing zone, is much easier to hit with, and has a chance of knocking your opponent into the air, which leaves you in a good position to juggle.
2) Against larger characters like DK, you can use Ftilt instead of Dtilt for your Flame Choke followup, which is much better as a kill option since heavier characters are harder to KO upward. At low % though, dtilt is better as it'll allow you to combo against some characters.
3) Avoid using Wizard's Foot as an approach against a character who is far away. Its end lag leaves you wide open on shield or miss if you end it right next to them. Grounded WF is better used if you anticipate your opponent rolling away from you when you're already reasonably close, because if they do roll backward, you'll hit, and if you hit their shield at near close range, you'll pass through them and be far enough away at the end that you'll be out of grab range. Wizard's Foot is a fantastic approach option against Ness, as it beats out PK fire and PK thunder, making it much harder for Ness to get damage on you, while simultaneously putting damage on Ness.
4) Aerial flame choke is not a good idea to approach from the air onstage. It's hard to land, and it leaves you helpless afterward. If you want to contest someone in the air, use Nair as a safe option, as it comes out fast, comes out twice, and has almost no landing lag. Plus, if you connect both hits, it does a whopping 21 damage. Fair is better at high percents if you plan on setting up a kill, but it's a laggy move that won't even come out if used from a short hop, so it's better used during a chase. Bair is also good, as it has very little lag, but it has a very short range, and requires some setup, so it's better used to edgeguard someone that's going to try to jump up from the ledge. Short hop Bair DOES work against larger characters like Donkey Kong, but it will go right over the heads of most characters on the ground.
Thanks, but what do you recommend I use to approach?
Nair is a better approach option, as it has very little lag. You can also cancel the landing lag of any full hop air attack with any B attack, but you must press A as soon as you jump for this to work, and you must do the entire full hop, so this takes practice.
Don't be afraid to throw out jabs, tilts, and nairs that are just short of the enemy. It might scare them into shielding, which will allow you to grab, or it might bait them into approaching when it isn't actually safe. If they approach for a grab out of a whiffed nair, answer with Jab, as it comes out fast enough to stop a grab and pushes them far enough to follow with a dash attack, which has a few frames of super armor when the hitboxes come out. Learn your tilt spacing, as well. If Ftilt is just barely short of your opponent, Dtilt will almost assuredly hit.