Particulate filters can be fairly cheap (fiberglass furnace filter) or very expensive (electrostatic filter).

I've DIY'ed a cast iron clawfoot tub in a rental 3 years ago and a fiberglass shower pan in my home 1 year ago.Both came out decent.

I use decent fiberglass tubs (American Standard).  

Next up is the fiberglass (better) window. 

That's using a GC and not doing much of the work myself (I only do tile work and TV/internet wiring myself), in New Orleans.The finishes are as follows; prefinished real 3/4" hardwood flooring (nail down), solid wood cabinets (flat packs from China), prefab 2CM granite counters (with SS undermount sinks), Frigidaire SS appliances, ceramic tile floors in bathrooms, ceramic tile tub surrounds, basic door hardware, recessed lighting living areas, smooth texture walls, builder grade interior doors and trim (door casing, baseboard and shoe molding only, no crown or window casing), painted hardiplank siding, builder grade vinyl windows, basic roof, fiberglass batt insulation.Our land costs are pretty cheap compared to west coast.  

The plumbing all roughed in and a new steel tub in one bathroom and a new fiberglass shower in the other.  

The results can be seen in the pictures below and final numbers at the end.Sheetrock work and then painting in the den and refinished the pine floors under the nasty pink carpet.Tore out siding on the porch and added sheetrock, installed new fan and light fixture, painted, closed in a window that looked from a bedroom onto the enclosed porch...Managed to save the cabinets, added granite and stainless appliances.Refinished the tub, kept the original floor and redid the subway tile in the original bathroom.Added this closet in the master, refinished the floors after ripping out purple carpet in here, painted walls, sanded and painted woodwork and added the fan.A laundry room no more, added this great bathroom onto the master bedroom.  5ft double vanity with granite top, toilet, free standing tub and custom shower.After having 5 tile contractors no show, either for the bid or after I had given them the job, I used a stock fiberglass shower pan from Lowe's and tiled the walls around it to avoid any more delays. 

You could pre-build wall or floor panels in your garage, and there are cheaper fiberglass roof tiles.

I managed a 120 unit property, all tile surround in bathrooms, Wow,, the mold, the grout issues, cleaning. wasn't the easiest. if we had to repair tile we just put in as close as possible never could get good matches.The owner recently bought a complex and put all new fiberglass surrounds.With a shower in your situation I would do the fiberglass stall, get the kind with that has like 3 parts the bottom unit, and the sides that fit on and around the base.

There may be some fiberglass in the ceiling joist and some foam under the rubber.