Yes, you are correct. 1 Vial is sufficient.
However, there are items that may or may not be included in the Vial; that's the capture device. This is something you will need to capture creatures. You will still be able to buy this in the Shop when the game launches.
I'm just buying a few more Vials to support the developers and also to speculate on the Alpha Vial's future secondary market value. 😅
Another thing to note is that even when alpha vials stop selling when the game enters beta and are replaced by beta vials (new starter creatures), you'll still be able to get capture devices there.
The main difference between alpha and beta will be the looks, we won't make capture devices "better/stronger" in the alpha compared to beta for instance. Even being able to craft capture devices players will be able to craft the same rarity/stats as those being sold so it's pretty much all about collector's choice and having a good start of the game with many items to aid your journey before professions are learned and skilled up, materials gathered, and eventually items crafted that match the ones that can come from the vials.
We don't want to make this a "pay2win" kind of thing where the project/company sells higher stat items just to fund the project, players will however need to burn zing in order to progress with professions and things all along while earning zing in different ways.
So in terms of the alpha vials, the looks themselves will be locked, beta vials will have completely different designs and even the capture device my not be a "handgun that shoots laser" but something else, hence the naming "device". ^^