you can get BTS without Warlords. I would recommend BTS, I just wish I got it sooner. The new features and units are very nice.
another thing to consider is it seems most on here have BTS so when reading posts and asking questions you will be comparing apples to apples.
I also just got the BUG mod recently which is also very nice. It does not change the gameply, it let's you see the information about your game easier. For example, it will tell you when your city is about to become unhappy, when a city is about to shrink. It also gives you info about the AI civs that you normally have to talk to them to get. So instead of talking to them every turn to see what they are up to you can just look at their stats on the right. One thing I just learned is, when you ask an AI to declare war on someone, if there reason not to is "We have enough on our hands already" that means they are plannning a war against someone already, it could be you or another AI. In the BUG mod, a little fist pops up next to their name on the lower right of the screen. I find this info very helpful and its all stuff you can get on your own, it just makes it easier and let's you spend more time on other more enjoyable things.