I was the same when I tried tea for the first time! My best friend would always order an unsweetened black tea and I'd always comment and criticize her since I thought it was so bitter and distasteful. I currently drink both coffee and tea. Coffee was first and I have it much more often then tea since I have a cup every morning. I've come to love having an afternoon tea as it's a calming way to ease into the latter half of my day. Just like coffee, I slowly built my "tolerance" and adapted to loving the taste of tea. When I began drinking coffee I always put some sugar and then quite a bit of cream. As time went on, I cut back on the amount of cream/milk I use and stopped using sugar. Now I will order doppio espressos regularly.
As with tea, I started drinking it by adding sugar/sweetener and the stronger tasting the tea was, the heavier I added the sweetener. I was not a fan of black teas and only would choose from the green tea category. I don't know much about the difference between them also white teas and oolong teas. All I knew was green tea tasted better than black. One thing I do know is that black teas generally have more caffeine than the others. After a year or so I was taking black tea unsweetened I now will drink a hot or iced black tea in place of coffee anytime I want a boost of caffeine but not a coffee.
Moroccan mint seems to be pretty common and it is definitely one of my go-to green teas. With black tea I tend to prefer one that is fruity like a mango black tea. If not that, English breakfast is great and is very good sweetened too.