I've usually had a planted FW tank along side my reef system almost since the day I started reef keeping. Many years ago, I would have a tank set up as a typical aquarium. Growlux lighting, and an outside power filter. I'd keep plants in it, but I got only fair results. This went on for many years.
The I read an article in TFH about full spectrum lighting in planted tanks. At the time the only real full spectrum bulb available was Vita Light, and they were difficult to find. Stitching to that made the plants grow and I got some good results with val, java moss, java fern, crypts and similar modest light plants. Stem plants and amazon swords didn't do well.
As a note, those Grolux bulbs touted for years as plant growing lights are almost worthless for growing plants, and they also look very artificial. These type of bulbs are still shipped with your standard aquarium hood or reflector.
The next improvement was using Laterite in the bottom layer of aquarium gravel. This provided some good trace elements and such for the plants. It's still useful today. I was getting better results with the same plants.
The next major leap was starting to use dry fertilizers. By adding a balanced amount of nitrogen, phosphate, and potassium, along with some other minor elements called CSMB in the planted tank world, the plants took off. I also started using good root tabs in the gravel. This what what solved the amazon sword plant problem. Most plants can absorb nutrients from the water, but the amazon swords, and related species absorb a lot from their roots.
As a note, most liquild ferts sold in your LFS are almost worthless. They just don't contain enough of what you want and/or the balance of the ferts in way off.
The final step was pressurized CO2 and a UV unit. The additional CO2 is a basic food source for the plants, and the UV helps keep algae down. At this point the tank is very high tech and plants really grow. Most plants can now be easily grown, and it can easily become a jungle in there.
If I were telling someone new to planted tanks how far to go, I'd say you'd want to start with good lighting and filtration, good substrata, and use dry ferts. The other items, pressurixed CO2 and UV are optional.
Like reef systems, your LFS tends to be clueless when it comes to serious planted tanks. Expect to have similar issues with your LFS. Don't trust them until they prove themselves.
Lastly, depending upon what your doing, a planted tank can be expensive to setup and run. Not as bad as a reef, but it's not like a traditional fish tank either.
PS - if there is a whole lot of interest in planted FW tanks here, I'll start a new threat with this post.