Riding Namma Metro for the first time is straightforward once you know a few things that aren't obvious from the signage alone.
Entry and exit are tracked at the gate, not the platform
Your fare is calculated from the concourse-level gate you tap in at to the one you tap out at - not from which platform or train you actually board. That means if you board the wrong train and have to backtrack, you won't get double-charged for correcting course, as long as you eventually exit through the right gate.
Buy your ticket before the platform, not on it
Tokens and cards are sold at concourse-level vendors - counters and machines - before you reach the platform. There's no way to buy a ticket once you're already past the gates, so plan for that queue on your way in, not after.
Card vs. token: card wins for repeat riders
A smart card gets you a straightforward 5% discount over the token price on every trip. If you're riding more than once, the RBL Bank NCMC card pays for itself in convenience alone - you tap and walk, no queueing at the counter each time.
Tokens are tap-only
Unlike some cities where tokens get inserted into a slot, Namma Metro's tokens are tap-only at the contactless gates - just like a card. Use them within 30 minutes of purchase, or they expire.
Bottom line
Buy your ticket at the concourse before you head to the platform, don't stress about boarding the wrong train, and if you'll be riding more than a couple of times, get the smart card on day one instead of queueing for tokens every trip.