For certain recent events Ruby medals have allowed for the free acquisition of raider cards. Medals are typically obtained by defeating bosses.
The Thin Blue Line[]
60 Rubies: Guaranteed one of x3 Red Alert
230 Rubies: Guaranteed one of x5 Tracks
500 Rubies: Guaranteed one of x7 Prowl
Junkion Reunion[]
150 Rubies: Guaranteed one of x3 Sharpshot
750 Rubies: Guaranteed one of x5 Sharpshot
1500 Rubies: Guaranteed one of x7 Sharpshot
One Shall Fall[]
50 Rubies: Guaranteed one of x3 Starscream
150 Rubies: Guaranteed one of either x3 Starscream or x5 Shockwave
300 Rubies: Guaranteed one of x5 Shockwave
SOS Dinobots[]
45 Rubies: Guaranteed one of x2 Swoop
75 Rubies: Guaranteed one of x3 Sludge
400 Rubies: Guaranteed one of x5 Slug
1500 Rubies: Guaranteed one of x10 Grimlock
Also, during this event for the first time 100 rubies on the weapon bridge would get you an Episode Boss Weapon (although these were availble for free through regular points rewards). Raider (Dinobot) weapons were not available from rubies.
The Colossus War[]
50 Rubies: Guaranteed one of x3 Ramjet
150 Rubies: One of either x3 Ramjet or x5 Galvatron
300 Rubies: Guaranteed one of x5 Galvatron
Call of the Primitives[]
75 Rubies: Guaranteed one of x3 Blurr
400 Rubies: Guaranteed one of x5 Wheeljack
5000 Rubies: Guaranteed one of x10 Bumblebee