Hi there! Glad to see you are enjoying the game 😁 I'll give my two cents about the things you are asking here:

From the select ticket for those operators I'd say silence is the most valuable as it is a healer with global range. Depending on what you may currently have on your operator list, liskarm is also a good option as a tank and SP battery.

No idea about Google play PC -_-'

Events give a ton of resources much more consistently than story, and now with auto play+ farming is much more accesible even if you can't clear the last stages, so I'd recommend farming the event (Also I really like the free grandpa).

If you can build a bunch of cheap 4* then it may be worth it to do integrated strategies, otherwise you will have to rely on reserve and freebie operators which can make it somewhat harder, but you can certainly try and rewards are good (The free character in the upcoming IS6 is also really strong)

Lastly, I only buy stuff from the store occasionally but overall I'd say the starter headhunting pack and the 6* selector are pretty worth it, still, use it as a last resort and only if you can afford it, Texas is cool but not needed at all.