Hi Trisha & welcome
I was in much the same situation as you 2 weeks ago before I found this forum. I came from a Canon 35mm SLR over 15 years ago & then drifted out of photography. Over the past few years I've had a digital compact camera & an iPhone. I got the inspiration again recently & embarked on the sharp leaving curve to catch up on DSLR cameras.
The technical quality of a photograph is mainly from the digital sensor, then from the lenses. the sensor being the most important. Larger is better, so if you remember back to medium format cameras, they were always higher quality that 35mm. The two main sensor sizes in DSLR are FX - which is roughly equal to 35mm, & DX which is about 2/3 the size of FX. You can probably tell that FX is therefore higher quality than DX. But either would be much higher quality than a compact camera or iPhone which have very small sensors. Total number of pixels is much less important than sensor size. A 12mp DX camera will be much higher quality than a 12mp compact camera.
Unfortunately, sensors are very expensive & a camera with an FX sensor will be much more expensive than a DX. As an example, the lowest FX camera in the Nikon range (D610), is around twice the price of the highest DX camera (D7100) in the range.
Each range, the DX & FX has a small range of cameras. The DX ranges from the D3300, through D5300 to the D7100. Each camera offering better features, but basically the same sensor size. Likewise the FX range has the same larger sensor size, but the cameras have more professional features.
A further complication is the lenses. There is a range of DX lenses which are priced & aimed at the enthusiast. The DX lenses are cheaper, smaller & lighter relative to the FX range. The FX lenses have a larger range with 2 or 3 streams within aimed at enthusiasts, semi-pro & full professional photographers with prices to match. There are some of the best lenses in the world available in this range.
Your first decision will be whether to go with DX or FX. This is often set by budget, which is why several people asked this. If you feel it's likely that you will stay an enthusiastic amateur, or your budget is the controlling factor, then DX may be the way to go. Quality is very good & even starting at the D3300 you could produce very good pictures. If you feel that in the medium term you may eventually upgrade to FX, or you may want the option to sell your photographs or you want the very best quality, then start with FX.
Start by looking at the prices & think about where you'd like to be in 3 years time. At both ends of the scale, for a less expensive amateur route, the D3300 with a 85mm f/3.5G AF-S VR DX IF-ED Micro for macro would work well, for the best quality possible in DSLR look at the D810 with a 105mm f/2.8G AF-S VR Micro-Nikkor IF-ED.
Bear in mind that in 35mm photography we knew where we were with lenses. A 35mm was a mild wide angle, 50mm was the standard lens & 85mm for portraits. This is the same for FX cameras. However DX cameras need a bit of maths due to the smaller sensor. You need to multiply the DX lenses by 1.5 to get the equivalents in 35mm film photography. So a 35mm in DX is the standard lens (35 x 1.5 = 52.5).
Good luck & ask anything you don't understand. We've all been there!
