Buying groceries vs. eating out

Hello,

How much could someone expect to spend on 5 or 6 day's worth of groceries, for one person one meal a day? And say I went out to eat on the weekends, what is the average cost of a decent meal?  I don't like to eat fast food but also don't need a five star restaurant. 

I'll be in a suburb in Kampala.  Are costs higher in the city center vs suburbs?

Thank you.