Maximum PvE rewards for minimal time
There are 2 strategies here: either join ~8 hours before the 1st sub ends or join ~8 hours before the event ends.
The worst strategy is to join right at the start of the event. The early brackets will be full of people looking to maximize their points for alliance rewards. Everyone in the top 100 will be hitting their refreshes on time every 8 hours and a good number of them will be grinding their nodes all the way down to 1.
A fresh bracket that opens < 2 hours before the event ends will usually be a death bracket. Placement is up in the air right up until the very last minute. I don’t like joining these because any distractions can cost you a top placement.
Joining about 8 hours before the event ends will keep your points low enough that you’ll eventually end up in the lazy brackets (I don’t think these are true newbie brackets, but they aren’t veteran brackets either. note that if you follow the bracket threads in the event forums, lazy brackets are rarely advertised). This will give you 2 refreshes, which gives you a bit of breathing room so that you don’t have to grind super hard like you would for a death bracket. If you join when there’s about ~300 or less players, hitting top 100 is usually easy. I’ve been top 10 (good for 1 4* cover and 3 3* covers) a couple times now.
For new character releases, I like to join ~8 hours before the 1st bracket ends. This involves a large time commitment (4 refreshes for 24 hour brackets, 7 for 48 hours), but you end up with a Legendary Token at the end. If you’re in a lazy bracket, top 100 is pretty easy. I’ve hit the top 10 for multiple new character releases (Carnage, Ant-Man, Sam Wilson, TA Hulk, Ghost Rider, X-23, Nova, Quake). This will put you into the veteran brackets again, and it will take quite a lot of poor/no placements to get you back into the lazy brackets (basically, this can only be done about once a month).
Maximum PvP rewards for minimal time
For season events, my goal is to hit the 4000 point progression (10-pack). You only need to get 400 points in each of the 10 events to get there. This will get you 10 event tokens and 250 HP from the individual events plus a 3* cover, 50 HP, and a total of 11 heroic tokens (1 single + a 10-pack) from the season progression. I can easily hit 400 points in less than 2 hours. If you manage to get into a fresh bracket 2 hours before the event ends, that’s usually good for the top 100.
Fitting it into an hour
I would say that I average about 1-2 hours a day playtime. Rather than play a single hour each day, it will be 3-4 days of hard grinding for a new character release and then nothing but DDQ for the next few weeks. The late bracket I joined was stale? Oh well, better luck next time.