Many people find that at first the nutrition tracker takes quite a bit of time to use, but that over time (as you become accustomed to the system) it gets much faster. For now, what you might want to consider is using our Quick Track feature. That will let you track the number of fruit and vegetable servings each day by clicking an arrow (like the water tracker). You can also track fitness minutes on Quick Track by simply entering the number of minutes and listing the activity. A link with instructions to turn that feature on is here: www.sparkpeople.com/community/help_answer.
Regarding community use, that is a little more difficult to answer without knowing the types of things you typically do. If you are active in teams, you may want to pick just two and stay current with those. If you read a lot of blogs, you may want to set a goal to read/comment on 3 each day. Those are just examples, but if you only have 15 minutes each day you may want to pick just one community goal to focus on at a time.
Once you become more familiar with the site, you may find that you are completing QuickTrack and your community goal in a shorter amount of time--at that point, you can consider tracking more of your food on the main nutrition tracker (maybe even start with one meal per day until you become proficient, etc.).
I hope this helps!