For your summoners, its very optional to what you take, i like playing exhaust, but choosing ignite is up to what comp your team is. If you level your Root first, it would be nice to take ignite for the extra damage in lane/teamfights.

Purchase Order really doe not mean that much with this, you buy what ever is needed to stop your opponents. for these items I've listed, you may not get enough gold to buy everything, so just go for the ones you need, like aegis for armor and the aura.

as you go along, just buy the wards you need through-out the game, i haven't listed loads of wards through the stages because you should be buying wards anyway.

I may have muddled this up a little bit because i didn't do it through-out playing, but i would suggest leveling your root first, this helps with a little cc with chasing and helping your adc in lane. After that, level your Rampant Growth for the passive CDR (Cool down Reduction). Then your Deadly Bloom, just for that extra bit of damage.

As a support, you should generally be going into the utility tree for the extra gold and the free ward and biscuit. Then i go for the Offense tree for that CDR + Extra AP.

For Rune Pages, The Magic pen helps add a little more damage if lane phase, helping out your ADC. Gold per 10 Quints for the extra gold because you shall need a bit extra for wards.