u/LeadershipSmart3458

Hi, it’s been a long time since I had a single speed but finally got back to owning one again. Picked up a very cheap old Fuji Feather (no idea what year) and have got it to the point where it’s good for me to ride it. I’m looking to do some more but need some advice. 

First off, I’m keeping it single speed, I don’t want to go fixie (been there done that before), and I swapped out the drop bars for flat, I just prefer them and they work for me. New tires, grips, saddle and pedals (thing on stem is quad lock for my phone for navigation). 

So, I could go down an expensive rabbit hole with this I’m sure, but a few things I’d like to improve:

1. The seat post is a weird shape, I wanted to put the bottle holder there (currently in odd place but i find it easy to reach) but that shape is not helping, recommendations for what to replace with that is a round cylinder all the way up?
2. Ignore the cheap fender that is there at moment, it’s temporary. Assuming I will need them, which fenders would work well (they’d need to attach to brakes I assume as nowhere else to fix)?
3. The current crankset (last couple of photos) makes some noise, where i live are some hills but i will also do some fair miles on flat so i think i'm looking at either a 42 or 44 (rear is 16). I like the classic look of something like the Shimano Dura Ace etc (chrome/silver style) but starting the research i’m not sure which models or brands work with this single speed. I don’t want to spend a fortune (I’m not racing it on a track after al) but something decent and reliable as I will put some miles on it so what would people suggest (i assume i would need to replace BB, crankset and chainring)?

Thanks!