Actually the start of the timeline would really be Mike Baron and William Messner-Loebs, and there is a recently new TP of Flash (Vol 2) that starts with Wally becoming the Flash after COIE called The Flash: Savage Velocity. If you want a starting point I'd recommend there, but DC are lazy and didn't reprint the ones after, so your choices are to buy them for cheap single-issue or skip them.
If you want to read the best ones, I'd recommend going straight to Waid. Baron might be your kind of thing, but Waid is more widely praised. There's another writer between Waid and Johns called Mark Millar who worked with Grant Morrison, so I'd recommend buying their storyline to understand Johns' better. It's only one TP and quite good in my opinion.
If you're more interested in the newer Wally West, I'd start with Titans: The Return of Wally West, as that reintroduces him in Rebirth. I'd then recommend moving on to The Flash (Vol 5) #9, and while that's collected in The Flash: Speed of Darkness it's the only appearance of Wally West in that book. In that comic Wally meets the newer Wallace and becomes a mentor. Then you'll want to move on to the bigger storylines like Flash War, Heroes in Crisis and Flash Forward, and then start reading the current Flash title from #768 onwards (The current Flash title is at #768 because DC changed the numbering and counted all of the comics from each seperate series and then continued on from the 1960's series which hadn't had any new comics for decades).
Just a warning: things can get complicated. There are two Wallys. Wally West was introduced in The Flash (Vol 1) as Kid Flash, and when Barry died and Wally took over in COIE he became The Flash. Wallace West was later introduced in the New 52 as a new Kid Flash and everyone started calling him Wally. Wally West was then reintroduced in Titans as the Flash and so we now have Wally West as the Flash, Wallace West as Kid Flash, and a bunch of other confusing moniker conundrums that I'm not getting into here.
Thanks for @'ing me, Fate.