You need to use a good quality water based foam leather cleaner. Maxi cleaner if it really dirty.
DO NOT use anything containing oils, waxes or silicones. (Most 'conditioners' contain waxes or oils)
BABY WIPES are the worst thing you can use as they will destroy the finish on your leather. They are very strong alkiline cleaners to neutralise urine (acid) on babys skin so they are not the right thing to use on leather.
Saddle soap is too harsh to use on todays furniture.
A lot of leather wipes contain chemicals which will aslo destroy the finish or leave residues on the leather which will damage it. They are not cheap in the long run as you would need a lot to clean a whole leather sofa. A bottle of foam cleaner should do your furniture 1-2 times.
You should also follow this with a good water based leather protector which will act like a 'scotchgard' and inhibit dirt and stains from being absorbed and make cleaning easier the next time.
If the leather has dye transfer from clothing or is very very dirty you can use a stronger cleaner called maxi cleaner which will probably bring it up well but must be used with care as it is a strong product developed especially for this kind of problem.