21mths between my girls. My sister has 7yrs between her two. There is no right nor wrong age gap, it's what you & your partner are most comfortable with.
There is going to be 3 years between my 2 iv got a lil girl that is 3 in august and in the time iv been pregnant we have toilet trained her so wont have buy double the nappies and got her off bottles which she only had one at bed time and got he in her own room. She also starts school in september which is good but the only problem is im expecting my lil boy around the same time which makes me a bit nervous!! lol