Oof...good questions. I can't answer you for Shaco...so I'll give you just generalized tips.
When should you start to gank? Honestly it will depend a lot on matchups...but with Shaco you want to get pressure early...so make your presence known by the time you get both of your buffs...even if it's just letting them see you. Now...knowing when to gank isn't easy...pay attention to every lane before you make your decision. You want to try to gank a lane that's pushed in on your team...it maximizes the distance the enemy will be forced to back off which gives you more time to sink your teeth in.
Remember...if you show up and they're forced to burn a flash...that's a successful gank even if they got away with no damage. Mark down the time of the flash in your chat so you know how long his flash is down...just guestimate. Because their flash is down...it makes ganking much easier for the next 5 mins or so until it's back up.
Never gank a losing lane...if your bot lane is 0-6 combined....you ganking that lane and potential giving up a triple isn't worth it. Tell them to turtle and gank mid and top so that you can snowball your other lanes instead.
Yes you buy wards...but a lot of wards. If you have 75 gold on yea...pick up a green...pink up the occasional pink. Ward for your mid and top as much as you can though you don't need to over do it. A well placed deep ward will work better for them both in the long run. When you buy your sweeping lens depends on the jungler...for instance I wouldn't get it on Lee Sin til level 9 or so and only after my sight stone. As shaco though...it's very handy to have that vision control so you know they don't see you coming...I'd get it pretty early, maybe even on your first or second back.