How much time is 150 mb on a smartphone? Is it a decent amount or really little? All im really going to do on it is surf the web from time to time not to much and get some apps that may require internet connection.
150 Mb is a measure of data quantity, not time. You cannot express data usage in time. I can download 150 Mb in a few minutes one day and in an hour or two tomorrow. The two are unrelated.
150 Mb would probably be okay for day-to-day browsing, twittering, looking at Facebook, etc. I would save the downloading of apps for when you can connect to a wi-fi hotspot or router (which doesn't use any of your data cap).