Here is a secret about rabindranath kobita: you do not need to understand all of it. Nobody does, not on the first read. Even professors argue about what some lines mean.
Tagore wrote for decades, so his work is not one thing. Early poems are romantic and dreamy. Middle ones are restless. Late ones are stark, almost plain. Picking an era helps more than picking a famous title.
Beginners usually do best with the shorter lyrics. The long philosophical ones can wait. Read one poem, then read it again the next day. You will be amazed how much changes overnight.
Do not worry about the hard Bengali. Some words are old, sure. But the feeling usually lands anyway, like hearing a song in a language you half know. Context carries you.
One honest warning: the translations into English lose a lot. They are not bad, they just cannot carry the music. If you read Bangla at all, read the Bangla. Even slowly.
A good habit is one poem a week. Not ten. One. Sit with it. The people who rush through Tagore remember nothing; the people who go slow end up quoting him for life.
And if a poem bores you, skip it. He wrote enough that you never have to force it. Your Tagore and someone else's Tagore do not have to be the same.