Just a quick work in progress build for my trundle play in dominion, it is designed to be as cheap as possible in order to maximise the number of items I can get in a game as well as focusing on cool down reduction to increase trundles speed and utility. Armor and magic resist come up low but this build offers about 3.3k hp, 242 AD, 48% crit and 32% life steal(not counting the sanguine). With the ult trundle will be able to shred enemy armor and magic resist, while significantly bolstering his own(ult cool down will be about 38 seconds).

the pillar is really trundles focus for this build which can easily be used to separate enemies from their team block them from the point or save a teammate, so for this reason you want to focus on cool down reduction, with this build the cool down on pillar will be about 8 seconds(If I recall correctly). Trundle is naturally pretty damaging as well as survivable he is a bit slow when not on his contaminated ground which is less useful in dominion as the map is bigger and the movement buffs available to others will help them close the small gap you can create with it. However this is curbed a bit with the increased cool down at 9 seconds you can use contaminate more frequently.

Those aren't quite the masteries I play a lot of champions and don't have a free page to spare just for trundle its a slight variation of what I actually use, it is what I would prefer though. Those runes also could be better I know but I don't want to spend any more ip on runes or extra pages right now and they serve me well enough.

Everything is here is set except the last two items the executioner's and sanguine, I recently discovered I am a huge fan of executioner's especially against champions like Fiora(*****). It is a cheap item with life steal and crit and adds a second hand ignite ability which. Buying this item is pretty situational, that is why I tacked it and the sanguine at the end there. If it is something you will want grab it early on, the sanguine might be you're focus after the atma's before finishing the mallet if you get that far.