What should I buy?

Hi

if most of the work you do is drawing, I would recommend illustrator and the combination of the illustrator and Photoshop will be better

What kind of artist are you?  What kind of art do you like to do?

Photoshop and Illustrator are two completely different programs.  If you're not sure which one fits your needs then I don't think you understand what they do.  I recommend a bit of research.

I'm a huge fan of Photoshop and have used it for many years, but I'm not a traditional artist.  Although Photoshop certainly can do purely rendered art, usually people use some sort of photograph and/or vector art (like what you do in Illustrator), and modify that art, composite it with others, do layout, shading, etc.  If you want to start from a blank canvas and paint or draw then there are better programs out there, many of which are free.  Try a search for 'painting program".  You could use one of the free programs and put the money towards a Wacom tablet - a necessity for any kind of drawing art.  I even find it 'necessary' for Photoshop.

Download the trial versions of Photopshop, Photoshop Elements, and Illustrator and you will be able to decide for yourself.

Corel Painter might be what you want. Many artists use it with Photoshop.

Gene

Sounds like you have a good start.   The tablet is a must.  I started with a Bamboo too, served me well for many years.

I can't recommend any programs as I don't do digital (traditional) art, but I hear Corel Painter and ArtRage come up a lot.  I looked into it a few months back, just because I didn't understand what was different from what Photoshop (with tablet) can do, and what a painting specific program can do.  The painting programs add a lot of features to replicate actual mediums such as paper texture or paint blending.  If you're using "oil paints" in a painting program and paint with a color over top another color you can blend them in as you would in real life.  Photoshop can paint with opacities, but it'll only blend as much as overlaying two colors in digital RGB space.  It sounds pretty neat, but if you're like me and don't have any formal training in traditional mediums it doesn't really mean much.

Photoshop isn't going to give as many painting-specific options as a painting program, but it can do a whole lot of other things that the painting program can't.  Will you use these features?  Who knows, but if you wanted to get into other forms of digital art then you'd probably be adding a Photoshop type program in the future anyway.  Also, if you get serious into digital art work (read: do this professionally) your path is probably going to cross Photoshop at some point in time, so you'll probably want to be at least competent in the basics.

Just things to think about.  I can't tell you which is the best option for you.  If you're just looking for something to paint with there are going to be much cheaper options than Photoshop.  If you want to do more than paint, then you'll probably be looking at Photoshop sooner or later. 

Also test Krita, which is a digital paint application, and free/open source! Supports full 16/32bit per channel as well. ClipStudio I use for inking and other tasks, because ClipStudio supports full vector strokes as well (which can be scaled to any resolution without losing quality - great for inking).

https://krita.org/

CLIP STUDIO PAINT | CLIP STUDIO.NET

I've replaced Photoshop with Krita and ClipStudio for all of my digital painting and drawing (and a little bit of Photoline). All these apps have a much better feel than PS. Photoshop does not support any stroke smoothing (there is a plugin called Lazy Nezumi, though) - something I find essential in a drawing application. Krita, ClipStudio, Photoline, Gimp - they all support stroke smoothing out of the box. Photoshop does not.

Worse, Photoshop's drawing has a couple of serious interpolation issues - this becomes extremely problematic when drawing sharp lines on a zoomed out high-res canvas: Photoshop will then add rough kinks and janks to your lines.

This makes Photoshop completely unusable for me (in terms of drawing) - you can check what it looks like on this thread (at the bottom where I posted an example).

Brush strokes become jagged after a few seconds

I work with the latest Intuos Pro 5 Large Wacom tablet, btw.

Painter 2015 and/or Photoshop.  But both require a good deal of study to get into.  As has been said, many artists use both programs.

You could also get Photoshop Elements, which should have a large amount of the features you want for a fraction of the cost.  It also has a much easier learning curve.  I can't say I've ever really used it, as it's missing many features that I consider critical, but for drawing and some basic editing I'd imagine it'd be ok.  I believe that you can have a single layer in 16 bit, you just can't do multiple layers.  I'd imagine you want 16 bit for drawing to minimize banding.

Krita also loads up Photoshop brush *.abr files. As does Photoline, btw.