Ann,
Don's right, there are many options for you.
Excel can be a great place to start, especially if you know in advance how you will handle growth, if and when it happens.
Be aware that if you use Excel, there may be some issues in the future if your needs get more complicated. For instance, if you record more than one gift per donor, things can get complicated when tracking in Excel. In addition, more than one gift per donor can lead to complications if you ever want to move your data into another program. Here is some info on that aspect in
How to Plan for a Data Move particularly in the sections on how much data and what kind of data you want to move.
I come at this from the perspective of someone who works for a company who sells donor management software. One of the main things we do is help people deal with the issues of moving their data out of Excel and into something different. From that place, I believe that if you use it Excel, you need to know that certain choices may make your move into something else later down the line easier or harder.
Best wishes,