I know this might not seem to fall into the category of thrifty scrapping at first glance, but:
Buying a Silhouette Portrait in a very cheap starter bundle for 130â‚¬ about after Christmas 2014 has made it possible for me to add selfmade embellishments, titles and die cuts to my pages without having to buy these things. I can now make my own stencils out of cheap cardstock or plasic sheets from packages, cut perfect titles that say more than just "the best" "love" or whatnot, so I think it has paid off already. (In contrast to metal dies that only pay off when you use them a lot (maybe shapes for cardmaking), which I probably would never do. I get tired of supplies and how many layouts need a "love this" die? -- For me it was a bit of learning and trying to find out how to transform nearly any image into a cut file (there are several great tutorials on youtube), so if you are a bit computer interested this might be great. Or you look for the freebie cut files many blogs offer and use these.
Also having an office printer is great as you could print (and even heat-foil: https://www.youtube....h?v=g2ABXldEEv0 thanks to the awesome Jennifer Maguire) a lot of things yourself. Black ink is enough, just colour in with watercolours.
Stamping is another way to stretch your stash, having some versatile stamps and basic inks (watermark, or embossing and a good black pigment ink, maybe one more subtle light dye ink) as well as maybe clear, white, gold embossing powder gets you very far. I am greedy with my embellishments, so I like to add some interest or a "layer" with dye ink stamped bachground images, mostly with Hero Art Shadow Ink "Soft Granite".
Glossy Accents is another "investion" I never regretted, as it gives some 3D or sparkle to a project, it can turn any stamped image in a glossy die cut, highlights little polka dots on a PP very easily. And it is a great adhesive that comes in a handy bottle with a fine tip.
A watercolour set is another thing that gets you very far.
So if you can spend some money try to think of items that could be universal or make it possible to create whatever you want in multiples witout much further cost.
If you look for things you already have, scraps ... maybe use stitching to shake things up and add dimension, (water)colours, fuzzy cutting to give old papers a new look, selfmade embellishments (DIY paperclips?), layering with cheap/used printer paper and only have some small strips of PP be shown in the layering -- maybe on both sides to give the impression it was a whole sheet behind your photo, cut tags yourself, use ribbon from gift wrapping, sprinkle and spritz to fill the page ...