Interactive Brokers for dummies

Guys, while trying to execute my first transaction with IKBR, I am receiving various warning messages such as:

confirm mandatory cap price
cash quantity order confirmation
use or do not use IKBR Algo
being blind - not having access to real-time data

Is there something generally to worry about or to benefit from using it?
Fractional shares for instance - should be avoided?
Algo is a paid or a free service? access to “more real-time” data is also paid I guess… do you use it?

Generally how exactly shall be the order be placed, I always select limit and set a price equal or very slighlty lower that the actual price I am looking at… can you leave the “set a price” field empty for instance?

Thanks a lot!