FYI, Ahmad and Zarrin aren't American brands (I get them in Middle-Eastern stores here).
Don't be scared going into a tea shop: the point of going there is to try teas before you buy them. A proper tea shop will let you sample the teas.
Start tasting from the cheapest ones, find the kind you like, and then try the more expensive versions of that kind until you no longer can taste the difference.
With loose leaf tea, just brew it to instructions (again, tea shops will provide timing/temperature for multiple infusions) - and you can see and taste the quality with your eyes. I've never experienced anything remotely close to "20% twigs and dust" even in store-bought cheapest loose leaf teas - anything that's not in teabags usually unwraps beautifully.
Of course, get a ceramic teapot if you don't already own one. For temperature control, if you don't want to get a kettle with a thermostat, add a splash of cold water to the kettle before brewing green teas: if the water is colder than necessary, green tea will take longer to brew, but usually will turn out OK, but overly hot water can make it taste badly/bitterly (black teas are brewed with boiling water).
If you know people from China or Taiwan, ask them! Not everyone there is a tea aficionado, but those who are will be a great source of information (..and possibly samples, especially if they get to travel there regularly). And in any case, best way to find out about tea is having tea with someone who knows a bit about it.
To my taste, one can rarely go wrong with a Taiwanese tea (the ones that make it to the US at least). High-mountain oolongs are my favorite kind of tea currently, but it's just one kind.
But the only way to get into tea - just like into anything - is try, try, try. If you need ratings/reviews, there is RateTea[1] - you can go to any Asian store, grab a can, and see if you can find the description (although that website can be a bit snobby at times).
I second the advice others have given (go to any Asian store, grab any middle-priced package). I've found some great tea that way (and if it doesn't taste good - try another one!). Also, I had good luck with using Google Translate / OCR apps to decipher the labels.
Where are you located?
[1]https://ratetea.com/