I'm thinking of getting my first new lens and the one I'm thinking of getting is a 50mm f/1.8.

Honestly, I'm looking for any opinions for or against if this is a good or bad buy and do have a few questions about it.

My current cam is a 60d with a 18-135mm kit lens. Usual subject are anything that catches my eye really. Maybe a slight tendency for more nature/landscape/architecture shots

1) Is it really as noisy as people say when it is focusing? How does it compare with my kit lens in terms of focusing noise?

2) Would it be a good idea for me to buy this lens for practice with a prime lens? Do I even need to practice with a prime?

3) How does it perform under low light conditions? I'm thinking I'll end up using this more for dinner with friends and family or for some posed family pictures.

4) How much better is the 50mm f/1.4? Should I just skip this and use the money for a 1.4 even if I'm still learning about primes?

5) Is my reasoning for this good enough to get the lens? I like to think I have thought this one through, but I know I still have a lot to learn in terms of photography.

Unrelated to the above,
Any recommendations for a good general use/travel lens? This is still a long way for me, but I would like to know if there is any one particular lens I should save up for/target later on when I know what I'm doing. Also so I can save up a budget for it. Preferably an EF lens and not an EF-S lens since I can see myself buying a full frame eventually.

I'm thinking maybe one of the three below:
Canon EF 24-70mm f/2.8L
Canon EF 24-105mm f/4L
Canon EF 24-70mm f/4L

Thanks in advance for any help