After 50 years of shooting, I got my first dSLR 2.5 years ago. I had a great P&S but I asked myself,
What do I want to do that I can't do with what I have now? The answers were ultrawide, ultralong, low-light. Also, I didn't want to change lenses a lot in everyday shooting. So with my K20D, I got the DA10-17 fisheye zoom, the DA18-250 walkaround superzoom, and the FA50/1.4 Nifty Fifty. And over 150 lenses later, those are still what I use most.
The best place to start is with what you have. Learn the strengths and weaknesses of your fine lenses. Note which focal lengths you use most, which focal lengths do or don't deliver the image quality you want, and which focal lengths you WISH you had available. Where you go from there lens-wise depends on what you want (and can afford).
I personally don't like the 18-55 and 50-x00 2-lens kit because I do much shooting in the 35-70 range, and changing lenses around 50mm is a pain. With any zoom or prime (fixed focal length) lens, we learn to see what that lens sees. Some people prefer smaller visual ranges. I really like having an 18-250mm window on the world. But I also recently bought (CHEAP!) a used small F35-70 to cover that most-used range with agility. That narrower window on the world makes me concentrate more.
Almost all of my lenses are cheap used manual-focus primes. These tend to be smaller, lighter, faster, and MUCH CHEAPER than new autofocus zooms or anything else. And they impose a certain discipline, similar to your old black boxes. Instead of zooming the lens to frame a shot, I must zoom with my feet, which makes me explore different angles and perspectives. You will see much discussion of such lenses here and on other forums like the European-based
MFLenses.com which is dedicated to them. Whole new worlds await you!
And some of those worlds may be very very small -- macrophotography! Some say that macro shooters are the happiest photographers around. Whether with a Raynox adapter, or a dedicated macro lens, or a cheap enlarger lens on tubes and/or bellows, shooting tiny stuff is a revelation and a joy. We also have many discussions of macro gear and techniques here. Seek and ye shall find.
Welcome aboard and have fun!