You want to gank in time. Your burnout gives you some movement speed to get there but its not enough sometimes I recomend exhaust so when you get there it will be harder to escape, but usually there is a ward and by time you get there they are already gone. With Ghost you can run through the river and even if there is a ward if you can run fast enough even if they noticed you, you will be able to catch up to them and make them waste flash or harass or possibly kill them. Plus at bottom usually the support already has exhaust. The top or mid usually has a built in stun or slow to help you gank. That is why i recommend ghost on shyvana plus it helps to get away if you decide to counter gank.

get wriggles lantern as soon as you can for that ward... Right after rush for the Frozen Ice Mallet to slow enemies after you hit them for better ganks. If getting fed then get phage and possibly skip wriggles lantern. You need the boots of mercury treads for the tenacity if the other team has a lot of crowd control. The sunfire cape is amazing on her with her burnout and it does so much damage all together plus from ravenous hydra you have created a lot of crowd control and for the enemy to actually focus you instead of your main attackers which are your ADC APC. You want people off their back and on yours to win the fight as you turn into a dragon. You will probably never make it that far but if you can sell your lantern or sell it late game for wards or make a blade of the ruin king or maw of malmortius.