A simple one will do nicely, one that does basic arithmetic and square roots. Details will be discussed in class as each exam approaches. Let me assure you that the actual math involved in this course is rather minimal, involving no more than arithmetic and a little basic algebra, and the book and lectures will emphasize concepts rather than math. Also, don't let the prospect of using computers intimidate you. You will get plenty of guidance, and I think you'll see that it isn't nearly as difficult as you might have expected.
Earlier material forms the basis for what comes later.
The reason I emphasize this at the outset is that it is very important that you not let yourself fall behind. If you blow off some of the earlier chapters and lectures, you will find it very difficult to catch up later on. Similarly, if you try to learn all the material the night before the exam, you will almost certainly regret it.