Change one thing per step
The instinct is to buy five unrelated teas and try them all. A better first move is to pick two that differ in exactly one respect — sencha and Longjing, which differ in fixation; Bai Mudan and an aged white cake, which differ only in years; jade and roasted Tie Guan Yin, which differ only in roast. Each pair teaches you what one decision does, and that knowledge transfers to teas you have not met.
Explore along an axis you have chosen
Pick a direction and follow it. By processing: green, then yellow, then white, then light oolong, watching oxidation increase. By roast: unroasted high-mountain oolong, then Dong Ding, then Wuyi rock tea. By origin: three teas from one province. By preparation: the same tea brewed western, then gongfu, then grandpa style. Any of these is more productive than sampling at random.
Buy from people who tell you things
The useful signal from a seller is specificity: origin, harvest year, cultivar, processing, and what they think it tastes like. A vendor who states all five is making claims you could check against the tea. A vendor who says 'premium' and 'ceremonial grade' is not. This matters more than price — a well-described inexpensive tea is a better purchase than an expensive one described in adjectives.
Keep bad notes
Three words per tea and the parameters you used. 'Too hot, sour, 90°' is a more useful record than a paragraph of adjectives, because you will act on it. After twenty teas you will have your own vocabulary built from your own comparisons, which is worth considerably more than borrowing someone else’s.
Expect to dislike things, and record that too
Finding out that you dislike smoky teas or savoury Japanese greens is as useful as finding something you love, and it narrows the field faster. Nothing here is a test — a tea being celebrated does not oblige you to enjoy it, and 'this is famous and I do not like it' is a perfectly good tasting note.