Hey, I remember that age to be really tough in terms of sleep... For us, DS started sleeping about 11 hours at night from about 11 months (and some controlled crying, but only needed to for about a week - if you do go that route, recommend being consistent and patient, as tough as it might be in the middle of the night...).
Also for us, DS not wanting to sleep for one of his 3 naps meant it was time to drop one of them. I remember it being quite a challenge trying to get the spacings balanced, and if he wanted his third nap, I let him, but I also didn't force him to have a third nap if he didn't want to - would usually let him cry a little after his milk, going in back and forth every 5 mins or so for about half an hour or so, and if still not asleep would get him up.
Soft music worked very well for us for a while and would mean he would actually lie awake contented before falling asleep.
At 21 months now he sleeps for a wonderful 12-13 hours at night with 1 nap after lunch during the day, and he is even content when he wakes up, happy chatting to himself, so hang in there, bound to improve :)