IIRC the reason the seasonal ones are "recommended" is because they give you a higher tier of pebble payout for their respective rarity, which makes them one of the only outliers in terms of pebble/hour.
Most companions will give you the same pebble/hour ratio per 24 hours, the difference is whether you have to play with them 24 times (for the grey-rarity common guys) or 2 (for the legendary/kickstarter companions).
The seasonal companions pay out more like the legendary rarity companions per play, but you can play with them 4-6 times a day, so they end up paying out more. Whether this is actually intended or was an oversight isn't confirmed, but seems intentional for whatever reason.
As far as strategy goes... The only "real" strats are who you want on your Gauntlet teams and who you want to use for Hunting. Hunts take certain combos, there are basic beginner guides (tho most of them aren't updated anymore) to find for those. Gauntlet is similar, you'll want to adopt one of several strats, some basic guides also exist for those.
Another strat is frog farming, where you offset two 1-hr pebble companions with one 1-hr basidio/frog on dogs you want to level and release. A 2:1 ratio means you don't lose money playing with Nana, to make it easier. You won't really be making much a profit, but the point isn't the pebble profit, it's the dogs to level to 10 to release for knucklebone tokens to use/sell.
