Hi there! Fellow Disc as well here. Let me spew out some helpful links that I've accrued in the past few weeks.

• Legion Disc guide: https://docs.google.com/document/d/1NbsDtJLVZqNc87jFzt-6WlPL02JOYmwppS1INtjVQTw/pub
• Some theorycrafting numbers ("atonement theory") to better help understand the value of atonements: https://docs.google.com/document/d/1bYJ1KgX6cO6qHEoCVRTvsc0TCOYkQ_GUwUKd2672Ntg/pub**
• Mythic+ BIS list: https://docs.google.com/spreadsheets/d/1m9hJO3WLCK02eQyeBdfs5OvC2or9AbaDPkabPb896j0/edit#gid=0
• Disc trinket analysis for Mythic+ and EN (HPS and DPS): https://docs.google.com/spreadsheets/d/10_AGXsn80WSQUy2KVDRd6nuAtofl8jCvy1ZWit7fNs0/edit#gid=0
• Priest class discord: https://discord.gg/0f1Ta8lT8xXXEAIY

The only Weakauras I use are for tracking Atonement numbers and short-duration cooldowns (PW:S, Penance, Mindbender). There's a TOOOON of 'em out there though for tracking literally everything. From just a quick google, I found these:

• (I use a modified version of this) http://www.mmo-champion.com/threads/2033628-7-0-Priest-Weakaura-Mega-Thread?p=41504202&viewfull=1#post41504202
• https://wago.io/NJ1kJ05Nb
• http://www.mmo-champion.com/threads/2033628-7-0-Priest-Weakaura-Mega-Thread?p=41505158&viewfull=1#post41505158
• https://wago.io/EyPko0fO-

Personally, I found mouseover macros completely necessary for Disc. Here's a neat resource with copy/pastable macros that conditonally use either Disc or Holy spells, depending on your spec (e.g. Plea becomes Renew): http://www.elenaltarien.me/holy-and-disc-priest-macros/

In terms of what to look for in logs, some baseline examples include maintaining Atonement on the tanks, 100% uptime on Purge the Wicked on boss, mana consumption over the course of the fight (did you time burst healing with boss abilities effectively? did you space that out well over the course of the fight?), not using Plea after 6 active Atonements, PW:S/Penance/Bender on cooldown, .... I'm sure there's more.

Hopefully that's enough to get you started!