There's a couple of options there. First off, assemble as much as possible before painting - anything that's the same color like frames, engine block halves/cylinder heads, etc - glue them together and let them dry first. In fact, I often assemble things while they're still on the sprue so I can keep the parts labeled and provide a handle at the same time. Remember, there's no rule that says the sprue has to stay in one piece, so feel free to butcher it up as needed.
Another option, there's sets of little alligator clips with stems on them (check Amazon, there's tons of cheap options with little plastic bases for holding them like this). Then I put masking-tape flags on the stems and sharpie on the part number.
Take like 2 big knights, then 4-6 of the little ones to make an army. Armigers are objective secured, so you really need them. If you want a full 2000 point army, I'd go with a Castellan, a Crusader (the Canis Rex box builds this), and 6 Warglaives. The Warglaives are basically required to take objectives from your opponent, the goal is to just lock them down and prevent them from scoring for at least half the game, until they can kill all your Armigers.
Building / Painting, you want to build the "skeleton" of the night first. Don't glue armor plates on the legs or the arms, and don't glue the top of the carapace on. Leave them all off. Spray the skeleton with Leadbelcher, wash it in nuln oil, drybrush it with a silver or other bright metallic, then pick out details. Paint the armor plates separately, I use something like these to hold the armor plates while I spray them and paint them. Once the armor plates are painted, glue them onto the Knight, then apply decals and varnish.
You want to search for “alligator clips”. As for the base, you can DIY using card boards or buy a “cat scratcher”. The one in picture is Mr. paint station. It’s not very stable. I also have this one below which i recommend because it comes as a set and more stable:
GJJC09B 1PC Painting Stand Base and 20PCS Alligator Clip Stick Set Modeling Tools for Airbrush Hobby Model Parts New https://www.amazon.com/dp/B07FGDDR74/ref=cm_sw_r_cp_api_glt_i_YPC7X4MS7DKQ519YZNG2?_encoding=UTF8&psc=1
If you slice up a corrugated box you can make the holder by glueing strips together. You can also buy something like this: https://www.amazon.com/GJJC09B-Painting-Alligator-Modeling-Airbrush/dp/B07FGDDR74/ref=sr_1_3?crid=33347KYH9QZEN&keywords=painting+clips&qid=1636063721&sprefix=painting+clipts%2Caps%2C284&sr=8-3
I did like what /u/Astronopolis said. It's very doable and doesn't really cost much more. Just a bit extra time doing lining. I just use a normal black gundam marker for lining (GM01) , though for larger lines I will also use the Tamiya panel liner. But for this Zaku I only used the gundam marker. Lining can go a long way to making the model stand out more, even with more basic HGs. The skirts here in particular look nicer with lining. More complex HGs and RGs have more opportunity for lining and benefit even more with it. You can get a basic set of lining markers - I suggest black, gray, and brown - for not much, and they will last through several kits. Gundam marker liners are easy to clean too when making them look neater or getting rid of a mistake altogether. If you want to go with the Tamiya panel liner or pour markers, make sure you read some tutorials on it, because you'll need to use a thinner or other solution to clean it, since they will damage the plastic if not thinned.
A matte coat helps to make colors pop and remove the plastic sheen, but you can also try other styles of coat like gloss for different finishing effects.
I use the Mr Hobby "Mr Super Clear Matt", which you can usually get a can of in hobby stores or online for $10-$12. I can usually do several HGs and RGs with one can, though you'll obviously end up using more for more complex RGs and obviously larger MGs.
I recommend spraying each limb individually in order to get the best coverage. It's more time consuming but the results are better. I use a painting stand and clip set similar to this to handle each part when I spray them, and then leave them to air dry before assembling.
Ideally you should do it outside on a sunny day that's not too humid (ie not more than than 70%). This will prevent frosting and make sure the coat can set correctly.
Lining and coating are good way to make models look nicer, especially if you're going to decal them too. I have done it on all my models (which I have posted here too), and the results are great. It can complement a paint job or enhance the default look of the model if you don't paint it.
Got them on Amazon GJJC09B 1PC Painting Stand Base and 20PCS Alligator Clip Stick Set Modeling Tools for Airbrush Hobby Model Parts New https://www.amazon.com/dp/B07FGDDR74/ref=cm_sw_r_cp_api_glt_i_Q468Y02KY86Y3ZGCY3XK?psc=1
GJJC09B 1PC Painting Stand Base... https://www.amazon.com/dp/B07FGDDR74?ref=ppx_pop_mob_ap_share