I used to instruct (when I was in my late teens).

The most important thing is a pair of boots & bindings that suit the boots, these were things that I replaced every few years (Dad had me skiing as soon as I could walk - once I'd stopped growing I got "real" boots, I've not skied since double reconstructions on my knees - still have my custom made boots in the cupboard).

Some boots/bindings aren't suited to some skis. Also you will need to look at the type of snow you'll primarily be skiing on as each type of snow (slushy, powder etc) can "require" a different ski (not really but for fresh powder I always have to go for quite long skis & slush I've got shorter ones on, x-country 1 set etc - I used to have 5 different sets of skis).

If you're buying boots, get them mid season - as your calves change shape, they're not as toned at the start of the season & toned at the end, so mid-season always worked for me.