What most naturally follows?

How to buy maternity clothes while pregnant
Get the timing down.
If you're carrying a single pregnancy, you probably won't start to show until the second trimester. For the first three months, most of your clothes (except the tightest ones) will continue to fit.
When you do start to need larger clothing, the best strategy overall is to buy what you need as you need it. If your spouse or partner is larger than you are, consider borrowing a few of their pieces to bridge the time between fitting into your regular clothes and needing maternity pieces.