ShadowWulfe: Wow.
So I never got into Civ series. It's hard for me to get into these without a fixed campaign.
Is it entirely sandbox or is there some kind of campaign?
The campaign is part of the game itself.
Civilization is not a sandbox game, you can obviously try what happens if you don't develop technology, and start just fooling around. You can even get relatively far that way too, as surrounding events are random, but you can't win the game by playing a sandbox game.
There are several ways to win the game, and which one you attempt to achieve also defines how your campaign will be like. Obviously the game doesn't give you any tips or feedback, you need to do it on your own.
You can try to achieve world domination by conquering all other countries, in which case it is easier to build fast-moving military and do it early in the game, when other countries haven't spread out far and wide on the map yet. Or if you try to achieve victory by building a space ship to Alpha Centauri, you need to develop science and have many cities building different things in the technology tree, and in the end different space ship components.
So which winning state you are trying to achieve is also going to define how the game will be for you and how you play it. It's different from let's say SimCity, where you can just keep building stuff for fun. Such a mode isn't part of Civilization, the original game at least, I haven't played every sequel so maybe one of them has it.