Hi and welcome to BrillKids
I started early learning with my son when he was 6 months old. The best advice I can give to you is to make the lessons fun. Be energetic and your child will vibe off your energy. At first my son was not interested in little math but after a couple of trips to the playground and joyfully yelling about how much fun little math or BrillKid numbers is he loved the lessons. Even if your child is not paying attention don't give up at least they are being introduced to new vocabulary and the info. Is being absorbed. Here are a few links that might have more ideas for you.
http://forum.brillkids.com/teaching-your-child-to-read/how-to-make-your-3-year-old-concentrate/http://forum.brillkids.com/little-reader/how-do-i-get-my-25-months-old-daughter-to-be-interested-in-little-reader/http://forum.brillkids.com/teaching-your-child-to-read/how-to-teach/http://forum.brillkids.com/teaching-your-child-to-read/difficulties-with-flashing-words-to-4-mon-old-help!/
In regards to your question about if should you be doing more you can look through the posts on product reviews and discussion to see if any other programs, toys, DVDs etc. will fit into your needs and schedule.
You can also incorporate early learning throughout your daily activities through talking and playing. When Cayden was six months old I started teaching him letter sounds with silly made up rhymes about the letter. I also read to him from my old textbooks and on various days pretended to be a scientist, lawyer, dr. Etc. to introduce him to words normally not spoken. I think I should start doing that again
Look forward to hearing more about your early learning journey.