Either 18/8 or 18/10 is good. The second number indicates the percentage of nickel in the product. The higher the number, the more rust resistence, so "10" is somewhat better than "8" in that respect, but either is good.

But those numbers don't indicate the weight of the pieces, or how they feel in your hand, so I'd recommend you look at several manufacturers and patterns in person to get a sense of what style you like (casual? formal? traditional? contemporary?). Hold the knife, fork & spoon to see if you like their balance. Will the size & design complement your dishes? If you want to wash them in the dishwasher, make sure the pattern you select is dishwasher-safe.

Once you've identified a pattern, you can do your price comparison shopping. Flatware is usually sold by the number of place settings (for 8 people, etc.), so make sure you're comparing like sets. A "place setting" is usually five pieces -- dinner knife, dinner fork, salad fork, tablespoon and teaspoon (not iced teaspoon). Also check to see what additio.nal types of accessory pieces are available for that pattern These may be called "completer" or "server" or "hostess" sets.

p.s. If you order online, be sure to check & factor in shipping prices, if applicable. You may find a local store that has what you want at a good price. If so, perhaps your mother could get you a gift certificate for that store.

We got our most recent set at Costco. It was by Hampton, it's service for 12 and 6 serving pieces for under $100. Hard to beat so we bought two sets and have service for 24. Then I never run out. We thought it was so nice we bought a set for my parents too. I have a set of sterling for good use, but tend to use the dishwasher friendly stainless almost daily.
Frankly, I had a Gorham stainless set that I bought at a fancy Beverly Hills China shop and when I needed more (kids!) the pattern had been discontinued. "Replacements" had limited stock at exhorbinant prices so I chucked it and bought this stuff. It was a frustrating ordeal. At the time I paid over $350 for the set of 12 and in today's money I'm sure it would have been over 500. I just can't see the point.
If you want someting more modern or finer, try looking at Ross Simons online for good prices.