I eventually want to own one, but would like to go up in size gradually because I feel budgie to macaw is a bit too much of a jump and would love a kakariki
Also, since you listed size as a factor, it is worth mentioning that kakariki are relatively small parrots, not that much bigger than a budgie. If your intention is to get a medium-sized parrot, you would need to consider other options.
For the sake of comparison, budgies tend to weigh around weigh 30–40 grams. Kakariki weigh around 65 grams. Cockatiels weigh 90-100 grams. In contrast, blue and gold macaws weigh approximately 900 to 1200 grams! That's over 10 times bigger than a cockatiel and a whopping 20 to 30 times bigger than a budgie.
Basically, kakariki are not that much larger than budgies. There is enough of a size difference that it would be better to keep them in different cages but budgies and kakarikis are similar enough in size that they could be allowed to share out-of-cage time under supervision. They are much, much, much smaller than B&G macaws and even significantly smaller than cockatiels.
So if one of your reasons for getting a kakariki is because it would be one step closer to owning a macaw, be sure to realize that it would only be a very small step. And also that macaws live for 70+ years, so when your are eventually ready to get one, consider adopting an older macaw. Otherwise, it is going to outlive you by several decades.
If you are serious about owning a large parrot, many macaw owners recommend doing the necessary research to understand what you are getting into and preparing your life as best you can for the life-long commitment involved with macaw ownership. After learning what is required to keep a macaw happy and visiting rescues, bird stores or breeders to meet actual macaws, you might decide that a large macaw will not fit with your desired lifestyle. Or that you need to wait until your life is more stable before making that kind of commitment.
It is generally a bad idea to buy a smaller parrot to prepare for owning a larger parrot, like a macaw, because most parrots have very long lifespans and different sized parrots are typically not compatible due to safety reasons. So you would need to have multiple cages and manage separate schedules for the differently sized birds, reducing the amount of time and attention available for each bird. In the long run, it is much harder to keep big and small parrots together, rather than sticking with a single species, large or small. So if your goal is to own a big parrot, think big from the beginning - do your research and be realistic about the amount of time, space, and money involved in owning a large parrot.
If you know that it will be decades before you will be ready to own a large parrot, you could get a smaller bird so you are not living without parrots while you wait for the right moment, but just be aware that, whether it is a budgie or a cockatoo, owning another parrot is not going to prepare you for macaw ownership. Meeting real macaws and talking with actual macaw owners will teach you much more about what you need to know.