I have a 3 yr. old 50 gal tank with 2 Calico Ryukin, Oranda Pearlscale, Blue Oranda; there are bunches of Java Fern, Anubias (nana, barteri) on a piece of wood and several groups of Crypts and 3 onions in the Flourite/gravel substrate.
The plants are both for aesthetic and purification purposes. The tank is primarily for the Goldfish.

If I use Prime (or TLC) dechlorinator and Seachem Gold Salt & Gold Trace, what is the basic care I should provide for the plants. Nitrates average ~ 10/ppm.

I am only a newcomer to aquarium plants myself but I believe that the plants you describe have fairly minimal light requirements. I know that the java fern does for sure- I have it and it does fine in low light.
Other than that I think trimming when needed and some people add CO2 and plant fertiliser. I expect someone with more experience with plants will get to you soon with more info .

I have kept all those plants myself,and they are rather easy to maintain in a regular tank with standard lighting.I didn't even feed anything to them and they did well.I think the biggest thing that they have to face,is the Goldfish themselves nibbling on them. I use Prime myself,so that wasn't a problem. I've never used the Gold Salt or Gold Trace though.How much salt do you use?

I use salt off and on; not constantly, and Seachem recommends 1 Tabl./10 gal.