When parents first begin signing they often get scared to use too many signs, but it’s usually better to start with at least a handful of signs, and sometimes even more at the risk of having too few signs. If you start with limited signs then you might not use a sign that represents your baby’s interests and your baby might not be motivated to sign it back.
Using more signs also teaches your baby the habit of looking to you to watch you sign the words. If you choose lots of signs, then there is a good chance that something you say will tickle their fancy. Think of signing like spoken language where you wouldn’t put limits on how much a child is spoken to out of fear of confusion, and certainly, a baby wouldn’t be expected to learn to talk only hearing a word being said 1-2 times each day with the rest of the time being devoid of any talking whatsoever. That why, there’s ultimately no reason to suggest that there can be too many signs.
Deaf parents sign all the words to their babies, and have been shown to sign back faster and increase their vocabulary at a greater speed than hearing parents who don’t teach sign. For non-deaf parents who aren’t totally familiar with signing, struggling to keep up with ASL as they went through all their spoken words would certainly delay their child’s signing rate though. Signs would become inconsistent at best and would more than likely be given up. Keeping up with a deaf parent who signs every word would be overwhelming for both you and your baby, and for this reason, is not recommended.
What is important with signing to babies is to be consistent with whatever signs you use, and start with any number of signs that you can keep up with on a regular basis. Of all the signs you use, a baby will pick which signs they want to adopt, and use those first. Having more signs than fewer signs increases the odds that your baby will find one that tickles them, and motivates them to communicate.