Best Buy has a couple good choices right now for $200. One is the Asus ZenPad with a 7.85" screen. Quad core Intel Atom processor, 2gb RAM, 32gb storage (plus microSD slot), and front-facing stereo speakers. The screen is very high resolution 2048 x 1536. The Samsung Tab Pro 8.4" is on sale for $200. Quad core 2.3GHz processor, 2gb RAM, 16gb storage (plus microSD), and 2k resolution screen. The main difference between the 2 is the screen ratio. The Asus has a 4:3 ratio (same as iPads), which is great for web browsing or reading eBooks, while the Samsung has a 16:10 ratio, which is better for watching videos (movies, Netflix) or playing games.
Personally I like the ~8" form factor for tablets. 7" is just a bit too small, and 10" tablets are typically too big to hold with one hand comfortably for very long. I have the LG G Pad 8.3, and it's the perfect size. I plan on replacing it with the Samsung Tab S 8.4 (different than the Tab Pro 8.4 I'm suggesting for you) as it's aging in hardware (and the battery is crapping out), but I've loved it in the time I've had it.
I heavily recommend spending a bit more than your $150 and going with one of those I mentioned. For $150 you're going to be looking at underpowered, older, underspec'd, and/or used/refurbished devices. The budget Samsung tablets aren't worth owning, with very low resolution screens and inferior hardware. Used/refurb'd tablets like the LG G Pad 8.3, 2013 Nexus 7, or older Samsung flagship tablets can be found in this price range, but you have to either hunt down a used one that isn't abused, or deal with the caveats of refurbs.
The Kindle Fire tablets are a possible choice. The main advantage (price) is also its main disadvantage. As Rupestris said, the Kindle Fire doesn't play well with Google (despite running a fork of Android OS). You're limited to the Amazon ecosystem, which wile fairly rich, doesn't compare to Google Play (or iOS). So if you're expecting popular Google apps, or the latest most popular games, you'll at times be disappointed. But for casual use, pretty much all the big apps will be available. The advantage is that since you're locked into Amazon's ecosystem, they can offer your a cheaper price on the hardware. In the long run though, I think it's better to go with an Android tablet since you can always install the Amazon apps and use their ecosystem, as well as Google's.