I'm a thin file with almost no personal credit history, who used an AU card to bolster my credit scores as well. So my experiences and research might help.
First of all, AU cards do help with utilization. But they help with overall utilization, not with the individual utilization on other cards. Both matter.
Secondly, I agree with everyone else that the AU card with the high utilization is hammering your score. The one possible exception is if the card is really old and your other AU card is really young, in which case it could conceivably be propping up your score more than hurting it (due to the boost to average age). But that's unlikely, and not being able to control utilization is a real detriment, so you should probably have it removed from your file.
More generally, the boost to scores from an AU is nice, but it doesn't change the fact that you have no real personal credit history. That will be the deciding factor for most lenders, not your score. Ignore all advice about how someone with a score X should be able to qualify for card Y; it doesn't apply to you. You're effectively an empty file, and that means you should be looking at starter cards. Avoid lenders who typically want to see a year or more of credit history (Chase will not give you one of the Freedom cards, for instance), and avoid the more conservative financial institutions. I'd avoid AmEx, as well. Your income doesn't really fit the kind of profile they prefer.
So where should you start? Your first card or cards should be keepers, because as your oldest cards they'll anchor the average age of your accounts. This doesn't mean they have to be cards you'll use as your primary drivers over the long term (a token amount of spend works), but it does mean avoid annual fees.
Also, since you're a clean file, and the AU cards have made your scoreable, you should be able to qualify for an unsecured card out of the gate (I qualified for the C1 Platinum with no credit history or scores at all). If I were you, I'd still take a secured card if that's all they're willing to offer. Secured cards from a real financial institution are a better option than unsecured cards from a subprime lender. But I'd first try to apply for an unsecured card
Discover is one of the two obvious starting points. They like young files. The Discover It is a potential long term card with the 5% rotating categories, while the Discover It Miles is effectively a 3% in everything card for the first year (1.5% doubled). DPs are mixed about CLIs, but generally positive. The secured card seems reasonable, and graduates.
The other obvious starting point is Capital One. Avoid the Quicksilver One, because they'll never upgrade it and you'll be stuck with an AF forever. You might (?) have a chance at the Quicksilver for good credit (no AF, but no SUP). But the default is the Platinum. It has no rewards, but it's a real card from a prime lender, and you'll eventually be able to upgrade it to a Quicksilver (took me 6 months) or maybe even a Savor One. Though C1 is notorious for bucketing people -- my card certainly is. But I didn't have a credit score at the time, and you do, so there's a chance you might not be stuck with a very low credit limit forever. Their prequal tool is supposed to be fairly accurate, but remember your profile is an outlier, so who knows.
Another option is Navy Federal CU, if you qualify for membership. If you have a parent, sibling, or grandparent who was honorably discharged, that's all it takes. They don't have to be members, or even alive. They gave me a real card with a real limit, even though I only had 6 months of personal credit history at the time I applied. They don't seem to care that my score was propped up by an AU card. People seem to think the prequalification tool isn't that reliable, but their secured card seems reasonable, and graduates.
Local credit unions might be an option, but they'll probably want to start you with a secured card. If you have some history with them, that can help a lot.
You might also want to consider the fintech cards, like the Petal 2 or Tomo. They assess creditworthiness using things other than credit scores. I don't know a lot about them.
There's also the Apple Card, if you're in the Apple ecosystem. Another I know little about, but they seem friendly to people new to credit.
Finally, there seems to be a recent surge of lenders expanding into the starter card arena. Some are out, some are in the wings. Look around, especially if you have an existing relationship with a financial institution. Chase Slate Edge might qualify.
Normally, you'd want to stagger applications. Apply for a card, wait 3 to 6 months, apply for another, and so on. This gives you the best chances, and the best credit limits. But if you think you might apply for an auto loan in a year or two, you might want to apply for a couple at once, so the hard pulls will drop off sooner (HPs have no effect on your score in 1 year, and vanish entirely in 2 years). Three personal cards is a good target, because it's enough to practice AZEO, but I wouldn't try for more than 2 at once. Credit seeking hurts a young/thin file a lot more than an old/thick file.
