Fitness Noob needs help

SilverMiles

For awhile now I've been doing Wii Fit Plus and walking here and there. I admit I'm lazy and prone to going stretches of time without exercise. But I need help on how to do reps since I wanna add strength training to my exercise routine for a stronger core. I've heard having a strong core helps improve metabolism, and overall good health. so how do I reps right now I've started doing 30 sit ups and wall push ups a day 5 a week. I'm fairly weak so getting it done is hard for me. I heard you wait a few minutes between reps if so how many minutes and should I do 2 sessions a day that way I get in 60 wall push up and sit ups a day? Also what else can I add to my work out that won't be over doing it till I get stronger