Here is my $ .50
I would suggest buying the regular elite as it’s the single best value and will make a huge difference to you in this game. Two builders, double tokens, more resources, more xp per run, etc…
Now, if you get on a decent team with Atlas, and you felt so inclined, you might consider buying Atlas elite occasionally only. At the most you really only need to buy it every other week to make really good progress with farming shards and building troops. Gold is ok for your team but I never really had a problem farming that.
Edit: I forgot to say if you do buy Atlas elite you could buy it halfway through an event so you get the benefit through a portion of each in order to maximize your placement in all Atlas events and those rewards (especially timers). If I buy it I tend to buy during troop build and farm the heck out of shards to be used in crafting event. Only level legendary or better gear during event, craft constantly outside of event.
I agree with the sentiment that you should only open any chests during PVP as others have said. Obviously if you’re within striking distance of a prize then go ahead and open enough to get you there.
It’s a marathon, not a sprint. Pace yourself, be disciplined, rarely is it worth progressing past the individual 400 - 450 sigil prize in events. It just takes too much of your precious resources to get to the next sigil award. Avoid the urge to over level in the early months / years (yes, I did say it was a marathon).
It’s a fun game but at times to be a free or an “E2P” (person who only spends on elite) it gets to be a chore.
This season I have managed to finish the token boost (I usually get that early in the season) finished UVS and nearly finished the first page of Astrid (rider). I am already starting to save for next season by not using rubies (only use them for gold chests or sigil chests occasionally) and saving all bronze and gold chests from here on out.
There is no way I could finish the other mythic and in fact I don’t know what I will do with the rest of my sigils.
Red has a season planner thread out here ( Red's Guide to Season Planning )
In the early days it will be hard but you can do it.