What software can you use for managing your Adwords Agency. You are probably searching for software for your workflow, reporting, emailing, document sharing etc.
Build your site in WordPress. The most integrations and easy to use.
We recommend Google apps to manage your email, docs, files sharing and calendar. For managing Adwords account the adwords interface and the adwords editor can be fine for most campaigns/clients. When you manage larger accounts you may need a feed management system.
You need a billing app, like fresh books. If you are doing SEO work also, maybe MOZ, screaming frog or Majestic SEO is a good suggestion.
For managing day to day tasks , track time and for reporting to your clients we surely suggest our app Swydo.