Traveling the east side of Taiwan

Hello,
me and my friend want to go traveling in a few weeks, at first we planned to just start from Taipei (since she will arrive there at the airport, I’m already living here) and work our way down to kaohsiung while stopping in Taichung, Chiayi and Tainan. But now we kinda want to go down the east side, and then up again, because she has to go back to taipei for her flight back home. We want to stop in Hualien and Taitung, but I find it quite confusing when I try to look up how to get train tickets. Because normally I’m just using my easycard to get from one city to the next, and the card doesn’t work in the east.
Does somebody maybe have experience on how to get train or bus tickets the easiest way (and maybe also the cheapest)?
Thank you

First step: get a good guidebook.

To follow the route you’re proposing (which is highly worthwhile, in my view), you’ll be taking Taiwan Rail’s South Link line to get from Kaohsiung to the Taitung (Taidong) side–then local trains (or the faster Puyuma) to get to Hualien, then presumably an express train (again Puyuma, or a Taroko) to get back to Taipei. The last leg might be the trickest to book given heavy demand and the bad behavior of travel agencies in Taiwan. I’d book that last leg as soon as you have a sense of your itinerary.

Enjoy!

Guy