Yes you had to pay a pretty penny to be able to attack but even if you didn't want to do that you could just let her be on the field to intimidate your opponent
2 Coalossal 3 Coalossal V 3 Coalossal VMAX 2 Martial Arts Dojo 2 Magcargo 2 Oranguru 1 Diancie Coalossal is the last deck that's much more similar to its current Standard counterpart than anything more classic
The biggest thing to learn are which abilities you can trigger so here are a few great examples of allies with text that includes when, whenever, and at: Katara, Bending Prodigy, South Pole Voyager, Ondu Cleric, Earth Kingdom General, and Hero of Goma Fada
It had some obvious play in other formats early on as well, such as Affinity in Legacy and soon in Modern, but the greater uses were initially minimal
(I'm really hoping this is old text, and that trap trick can be reliably played with Reef and Torrential for maximum Umi)
It doesnt untap during its controllers next two untap steps