Originally Posted by
beermode
I just upgraded to a 10-52t SRAM 12 speed cassette to go with my 32t chainring, and I couldn't imagine anything lower. 30t and a 51t combo is overkill on the lowend. I couldn't imagine going slower than what I already do, keeping the front end from wandering about is enough of challenge. Going slower will make the wander even worse.
I would go for a quality fork first, assuming your bike has an entry level fork. If it's an older fork that hasn't been overhauled and rebuilt, get a new fork. It can change the way you ride, not just the rough stuff, but the cornering as well.
Look out for hub compatibility. If you have Shimano 11 speed, the NX cassette can fit since it uses the same hub, but not the GX or above, those require XD hubs. The new 12 speed Shimano won't fit either, those use MicroSpline hubs.
A 30 - 51 on a 29“ bike is similar to the typical 22 - 32 on a 26“ bikes.
If you don't need that sort of gearing, you don't have climbs steep enough. I prefer to pedal at 5kph if necessary rather than walking carrying a bike.