This time of year people advertise free top soil on Gumtree , and probably some stone if you wanted to edge the bed. If you’re lucky you could get a free garden bench or if you’re handy you could get some pallets and make one, painted same colour as bench. Or as above suggestion, make one from plant pots and wood - again Gumtree and Facebook your friend for freebies on this.
I'd look out for some cheap plants, and arrange in a grouping with either some or all in large pots. Turn it into a lush corner with a loose theme, and the plants may get a little more sun if raised off the ground.
I If it's really shady, I'd go for a jungly vibe... Fatsia Japonica, maybe a couple of ostrich ferns and a hosta (boring by themselves, but together can look interesting imo).
A dwarf acia tree could look lovely there, (a beautiful red or yellow one,) but might be over budget (you might be able to get a smallish one for not too much money though). Could group it with some bamboo (in a pot!) and maybe an interesting fern.
Small Hydrangea in a pot maybe? Or astilbe (bleeding heart) is lovely when in flower, especially the white one but can look a bit scruffy when it's finished.
I've picked up very cheap plants from garden centres before, often reduced because they look slightly past their "best" but perfectly healthy. Or baby trees/shrubs from supermarkets etc, which would look very underwhelming in the ground, but look elegant when elevated in a pot.
For cheap pots, either paint a plain terracotta one, or pick some second hand ones up.