I also had a hard time learning streams, here's what I did;
First of, you have to have patiens. It took me a few months to get the hang of it and I got frustrated when a long stream came in a map I was about to pass, but I tried to stay positive and stay motivated.
The best mapset IMO is this one:
beatmapsets/1056621#taiko/2246165 The two hardest difficulties should be good to practice on. The map features long, easy to read streams at 128 bpm, hence why this was my go-to stream practice map.
Other than that I would download these three too:
beatmapsets/1138198#taiko/2377792 ,
beatmapsets/432406#taiko/1302635 ,
beatmapsets/1206242#taiko/2512042 . These three are at a little faster bpms, so when I first downloaded them I played them all with the half time mod.
So in general, be patient, download long stream maps and play them with half time if necessary.
Hope this helps! ༼☯﹏☯༽