Everything should be done in steps and you stop when you are either satisfied or no longer interested. Some can learn for years of even decades I suppose but I have not been around photography that long!

Many people just starting on their are unhappy with their photography. In order the importants the problems lie with:

1. The photographer
2. The lens(es)
3. The camera(s)

Photography is an art and requires creativity but also technique in order to realize your vision and understand limitations. This is the first thing you must learn about. You can start with good books - many of them available for free at the local library - such as Readers' Digest Photography Manual, National Geographic Photography Field Guide, Photographer's Eye, etc. It is not a problem these books are older because the fundamentals are the same as before.

Once you learn from a few books you should really enroll yourself in a workshop. The ones I teach (in Montreal, Canada) go for 4 weeks and are a mix of lectures about the fundamentals, studio and outdoor practice. A bit of everything and mostly chances to systematically practice.

A lot of people show up to my classes with their gear already and learn part of the way that some other gear would have been better. That is because the right gear depends on your needs, the type of subjects you shoot and other considerations.

Your Nikkor 18-55mm is what is called a kit lens and is the bottom of the barrel in terms of quality and versatility. After learning more you really should replace it with one which suits your own requirements.

The Nikon D5100 is a entry-level DSLR but that mostly means it is slower to operate than high-end models. Image quality is very good and you can shoot anything well with that camera. Of course, higher-end models have plenty of benefits but it is unlikely to realize them until you get quite proficient.

Photo processing software is the last thing you should be concerned about. You should concentrate on making the best images first. You may decide after that you do not need to process your images or you will get some really good images to process. What I mean is that better captured images make better processed images!

Everything should be done in steps and you stop when you are either satisfied or no longer interested. Some can learn for years of even decades I suppose but I have not been around photography that long!

Many people just starting on their are unhappy with their photography. In order the importants the problems lie with:

1. The photographer
2. The lens(es)
3. The camera(s)

Photography is an art and requires creativity but also technique in order to realize your vision and understand limitations. This is the first thing you must learn about. You can start with good books - many of them available for free at the local library - such as Readers' Digest Photography Manual, National Geographic Photography Field Guide, Photographer's Eye, etc. It is not a problem these books are older because the fundamentals are the same as before.

Once you learn from a few books you should really enroll yourself in a workshop. The ones I teach (in Montreal, Canada) go for 4 weeks and are a mix of lectures about the fundamentals, studio and outdoor practice. A bit of everything and mostly chances to systematically practice.

A lot of people show up to my classes with their gear already and learn part of the way that some other gear would have been better. That is because the right gear depends on your needs, the type of subjects you shoot and other considerations.

Your Nikkor 18-55mm is what is called a kit lens and is the bottom of the barrel in terms of quality and versatility. After learning more you really should replace it with one which suits your own requirements.

The Nikon D5100 is a entry-level DSLR but that mostly means it is slower to operate than high-end models. Image quality is very good and you can shoot anything well with that camera. Of course, higher-end models have plenty of benefits but it is unlikely to realize them until you get quite proficient.

Photo processing software is the last thing you should be concerned about. You should concentrate on making the best images first. You may decide after that you do not need to process your images or you will get some really good images to process. What I mean is that better captured images make better processed images!

EDIT: To answer the newly worded title of your question, yes. Not because the D5100 isn't good (it is, all modern DSLRs are) but because you bought something without knowing what you need. It is possible you will discover the D5100 is perfect for you as it is possible you will discover there is something which suits your needs better. You also did not put any thought on your lens, arguably a much more serious error photographically speaking.