If u go for an egg ride a fast bird and look for high level eggs if u find a low level eat so it respawns stay away from lighting as they have a continuous line of lighting unlike poison and fire to get milk make a behemoth wyvern trap with a key pad as I have used that method and can confirm it is easier then just shooting with tranqs
If your playing by yourself or very few people all you need is a argy pumped with health, stam and melee and argy has tighter turn radius so you can fight wyverns without worrying about special attacks but in group stay in middle. Like so people can see
The best way to level up a Giga on Rag is to get a bunch of wyverns to follow you on your griffin/ptera, then dismount you’re flyer above the Giga, then get on your Giga and absolutely destroy them. This got my Giga 26 levels from 3 wyverns.