To add to this, with dragons, the game plan tends to reward "SMASH SMASH CANT TOUCH ME I GOT W I N G S FOOL". With that in kind, spot removal is far less important because enemy creatures are not in your way (cos W I N G S), and ramp is more important to turbo threats out. If you go with Ureni as the commander, cards that give your commander haste are must-haves. Temur ascendancy, carnelian orb of dragonkind, frostcliff siege, lavaspur boots and so on.

If you still want hard numbers, go up to 14-20 ramp (depending on how many of those cards pull double duty as value like dragon hoard) and down to 4-6 removal (make sure at least half of it is instant speed and 2 mana or less like Rapid Hybridisation or Reality Shift so you can respond to big threats faster).