Yeah I didn't see previous games. Just saw that a bit ago. But yeah, in 3's warding and counter warding is crucial. Even more so than 5's. Keeping Red warded will help you catch most ganks besides people like tryn who spin over the wall into the brush, and keep Dragon/top jungle on your mind. You can learn a lot from having Dragon warded, even if they just pass by it to go do buffs. Whether they bothered to ward Dragon themselves, whether they ward the bushes/where they specifically tend to ward, whether they are more likely to go up or around a buff/pass by dragon, etc. Just keep that in mind.
As for Dan specifically concerning Rumble, I wouldn't be so split on items. Scrap rushing Kage, even if you have a good start, and just get either:
1. Revolver
2. Work on Rylai's
3. Work on Death Cap
After finishing one of those, assess where you need to go. If you have another person who will like AP/Spell Vamp like Singed, have both of you get WoA. Double benefit for both of you, and smite will heal you. Basically, Singed/Rumble/lot of AP champs with 50% Spell Vamp can be quite annoying on 3's. I'd aim for that after 1 big item if you're going to do double. I'd also skip Revolver if you're having a bit of a slow start, and just aim for Rylai's/DC. You'll find that getting Revolver first gold wise will put you into a bigger hole than you want if you can't get on a roll.