Okay, so I don't have a ton of experience in Civ V but I typically do pretty well, until the end of the Renaissance or start of the Industrial Era no matter what Civ I play. What I struggle with is doing everything at once.

I'll often be beating the AI for quite a while in the first few eras, but then all the other Civs have somehow managed to pump out a huge army, settle like 5 cities, make a ton of gold, make like 20 wonders, keep all their citizens happy, and spread their religion like wildfire. I'm only playing on normal difficulty, so it's not like they're getting a ton of extras.

So what should I be doing in the early eras to prepare for the future? Should I do a lot of exploring, settle a lot of cities? Or do I go full wonder-whore and build up a huge military?

QUICK EDIT: I forgot to mention, I also am really bad at technology, I think. Like, I can never tell what tech I should I rush so I usually end up just doing all the tech in an era before moving on. Is there a general plan on what techs I should rush?