annoying newbie questions -shame on me- LONG

I used to have fish and plants in ..lessee.. I was 14.. I'm almost 53
now...1965!!! Old metal frame 20 and 15 gallons with white silica
sand and under gravel filters with vibrator pumps to get the water to
circulate through the under gravel filters, and a siphon over the back
filter.

All I had were 2 incandescent 15 watt bulbs and a little indirect
light from the front window and at that had crystal craze or paper on
the back and sides of the tanks to keep the algae growth down, and the
plants not only survived but MULTIPLIED!!

Now, I have four modern all glass 55 gallon aquariums and one 20
gallon and under gravel filters, natural river gravel, but.. what I
fear the culprits were.. power heads rated for the size of the tanks.
(Can't recall what they were now as they have been unused for some
years now due to my disabilities and inability to care for them at
that time).

I tried to grow plants for some time in there with the two 15 watt
florescent grow lights on the upper tanks, and two 40 watt grow light
4' tubes on the lower tanks. The 20 gallon had One 15 watt grow tube,
and it wasn't a show tank, just standard kind of blocky 20 gallons.
The plants grew best in that 20 gallon than in the 55s, but everything
else was rather pitiful, only able to occasionally keep a potted plant
alive. I love the plants as much as I love the fish.. mostly I like
the little tetras, khuli loaches and cory cats and pygmy cats and
otocinclus algae eaters, things that don't disturb plants much if at
all.

So, what would y'all recommend I read, look at, or can you tell me
what I'd need to get to illuminate standard 55 gallon tanks
sufficiently to keep plants alive, and I have "got it" that pretty
much power heads are bad, and probably undergravel filters are bad..
or.. if they aren't they're limited to the front shallow areas of the
tank that are generally left "open".

I have a Banche Reihl sp? Encyclopedia of Tropical fish that
somewhat addresses substrates and plant tanks, but I looked for the
substrates online and they were like $15 for tiny bags of it, I'd need
hundreds of dollars worth to put into just one or one and part of
another from what I'd figured, and so got depressed and quit looking.

Are plant tanks something only the rich can afford? I live on a bit
over $860 a month.. disabled.. has to get tanks moved before setting
up, so I figured I should start checking around a bit now.

I know.. lot of questions long post.. whip me now hanging head in
shame but I wanna knoooooooow and I know I don't know enough anymore
to phrase a short question.

Janice