Once you buy Hunters Machete and the Rejuvenation bead go for the blue sentinel cause he gives a health and mana buff hold tab and look up to see when dragon spawns hold mouse over the icon to know which dragon and same with sentinels also W has no effect on anything in jungle but E and obviously Q do. So if you want to upgrade W before E thats fine depends on the situation. If you don't know how to play Galio cause you just bought him I recommend you watch the Galio hero spotlight on the League of Legends Youtube channel.