Beginning readers benefit from learning more than one letter phonograms early. Phonograms are defined as one or more letters that represent a sound. Lately on most Fridays I make a Phonogram Friday post for anyone interested in teaching phonograms. Here's a post with free common two letter phonogram flashcards for you to print and use.Here are some videos you may find useful if you are teaching phonograms.
Here's a link to Bioline Educational Resources' blog Teaching Ella to Read.
I found a post that suggests teaching babies and toddlers phonograms and words. If a toddler shows interest in learning the alphabet, I think teaching more than one letter phonograms would be a good idea too. I suggest allowing a child to practice and really learn a few letters and phonograms at a time. Here's a post I made showing ways you may want to teach and practice letters and phonograms. Phonograms and Blends