I'd suggest sorting out what will do well in the winter shade right against the building first. Kangaroo Paws will grow just fine there, but really bloom best with full sun. Most of the Kniphofia/Poker Plant cultivars will also bloom best with full sun. You also have an Angel's Trumpet/Brugmansia at the left side of the unit, and this can get quite big over time, but can easily be trained to be a multi-trunk tree, and will be bloom well in these light conditions. The cultivar 'Charles Grimaldi' is my personal favorite, and has a warm orange shade of bloom. I'd also suggest that some really big ceramic pots at the walls flanking the steps, with a colorful foliage plant such as Phormium 'Yellow Wave' or 'Cream Delight' could give you year round color, as well as foliage texture. Alternatively, you could also use specimens of Strelitzia reginae or Euphorbia cotinifolia in pots, perhaps with trailing Euphorbia myrsinites, or succulents such as the lavender tinged Graptoveria 'Fred Ives' or Echeveria imbricata. If you wanted another larger growing shrub with nearly year round bloom that could be kept relatively narrow, the Princess Flower/Tibouchina urvilleana does really well in southern California, but does need regular watering to bloom well. The Mexican Lobelia is also nearly year round blooming and grows well in shade and with little water, and can be sheared into a hedge and treated like boxwood. You might also consider using a bold foliage plant like Giant Walking Iris/Neomarica caerulea, having a similar form to a Phormium, but with waves of deep purple blue flowers on 5 foot tall stems all summer into fall. Another really cool shrub with purplish tinged foliage and blue flowers in late winter/spring is the uncommon Ageratum corymbosa, which also does well in light shade. Kalanchoe carnea modoc is another sculptural succulent that is winter blooming, takes shade, and would do well at the front of your building. With the formality of the building facade, I would suggest that treating it as a formal symmetrical planting and massing foliage plants with some color would give it a more integrated look in the front. You might also consider Reed Stem Orchids, Epidendrons, for a narrow yet tall and everblooming airy plant. Some narrow growing palms such as Chamaedorea tepelejote or C. plumosa could also look cool in front of the building, and will do well in shade, without getting too big. If you want to do the Gingers, they typically do want more regular summer water to do well, but things like H. greenei, H. gardnerianum, Alpinia zerumbet variegata could combine well with the Brugmansia and Tibouchina water wise. I wouldn't recommend planting the Horsetail/Equisetum unless it is contained at the roots, as this is a rampant spreader and will choke other plants out over time. You could plant the similar appearing South African restio, Elegia capensis for a similar look, which is very lacey and ferny foliage. Asparagus retrofractus is another tall ferny/lacey looking plant that would like these conditions. Good luck with the project, and post some photos of what you decide to do!

I think the easiest way to maintain a large area is to create a woodland environment. Separate the 'woodland' from the 'yard' perhaps with the wall in the picture, or by some sort of border like logs or simply the edge of the lawn, and don't worry too much about maintaining the woods. I am sure you've seen yards that border the woods, and some of them look perfectly manicured despite the fact that nothing is done to maintain the woods. So, it is partly attitude ('those are the woods, this is the yard') and partly a good border between the two that makes your life easier. I would start by by mulching and planting large clumps of a few types of shrubs or small trees. Pick out perhaps three to five types of native woodland shrubs. Get perhaps three to five plants of each type. Plant each type of plant in an informal clump. The clumps should be arranged to look nice, frame in your yard and woodland path, and to not interfere with each other too much (give them the room they need). In general, put taller ones toward the back, smaller ones in front. Mulch the whole area. You can buy shredded bark or find a local tree trimmer or the municipality who shreds branches (power company crews, road maintenance crews etc.) and sometimes get the chips for free. i would use the most natural-looking mulch you can find, so that the woods look as woodsy as possible. in the future, simply leave the leaves that fall. You should probably mulch again in future years to help build ip the soil and supress weeds. I would probably remove a lot of the small plants that are there now. I see a yellow-green groundcover that is probably a sedum, some weeds, I think, and some grass. none of these really fit in a natural woodland, so I wouldn't keep them. As the shrubs grow, the spaces in between you can plant with wildflowers, ferns, etc. Once you get the shrubs growing and a good mulch on the soil, you can take your time (years, if you want) planting wildflowers, and I think you'll enjoy it. I would start with several Flowering Dogwood (Cornus florida) scattered through the woods. I would plant clumps of Cranberry viburnum (tall, put it near the back), American Holly (Also tall), Maybe Gray Dogwood in the sunnier parts of the front, Blueberries (highbush type- most of the blueberries grown for fruit are 'highbush' blueberries that will get four or five feet tall, at least), and perhaps Red chokeberry, or maybe Inkberry holly, which is evergreen. I would make each clump something like 10 ft by ten feet, but an irregular shape. This will fill a lot of space, you'll like the look of the shrubs, and there will be no maintenance - you can simply let them grow once they are planted and watered for the first few months. I think evergreen groundcovers are a pain - weeds often grow through them, it is hard to get leaves out of them, and unless they grow really thick, the look like a poorly maintained planting. Woods, on the other hand, aren't supposed to be maintained and so look fine full of leaves and sticks. Just maintain a path through them and you are fine.

I would start with hardscaping to create a little mystery and anticipation in that flat plain. For example, you don't need to know much about masonry to lay out and construct a curvaceous and intriguing path of dry-laid brick or flagstone with perhaps an arbor to mark an entrance, a berm or speciman boulders to add some contour. Once you have the backbone in, other ideas begin to suggest themselves - such as a serpentine border of low groundcover along the path, a vine climbing up the arbor, plants with complementary foliage paired with the rocks, and shrubs or grasses to coyly disguise your path's progress (where does it go next? let's follow it and see!)

A machete? Scythe? This thing: https://www.homedepot.com/p/Ames-Double-Blade-Weed-Cutter-2915300/204476217 Okay, maybe not a machete ... but there's probably a similar tool that garden centers do carry. And Home Depot also carries this scythe: https://www.homedepot.com/p/Razor-Back-12-in-Grass-Hook-with-Wood-Handle-62220/303209945 You'll also want a heavy duty shovel for getting invasive roots out, though some vines are actually easier to yank than dig. We picked the double blade weed cutter when we were dealing with an overgrown area. Stand clear when someone's swinging ... its vicious. Whack the mess to a manageable height (to the ground), dig out as much as you can, and cover with heavy black plastic to sun bake what's left. You'll still have some come back that you'll have to keep after, but it should help with a lot of it. Watch out for poison ivy, and good luck!