painting can be so therapeutic and rewarding :)
i recommend starting with watercolor or acrylic as they’ll be the most user friendly. each has its own techniques and learning curves [ie working from light to dark with watercolors, acrylic pain drying darker]. familiarize yourself with their properties. you’ll need mixed media or watercolor paper pads, nothing crazy like canvas in the beginning, so you don’t feel obligated to reserve expensive materials for something “good”.
but, in the vein of not wanting to waste materials, make sure you don’t let your fear of messing up prevent you from painting at all. as an artist on a budget, i understand it’s a hard mindset to break. but i do suggest setting aside a little coin for nicer paints and brushes if you can, though. a lot of stores will have cost-friendly things labeled “student grade” which are decent quality. (things like the chalky artist loft watercolors or 50¢ loose bodied acrylic paints may add to frustration sometimes but they aren’t impossible to work with.)
the easiest ways to get yourself actually painting are to set up still lives or paint “en plein air” (landscapes outside). working from life is an invaluable skill and once you’re comfy with that, it will be easier to paint from photo reference. also, make sure you’ve got an understanding of value and contrast outside of color. make color charts so you understand how your paints interact with one another and you’re not in for a mixing surprise mid painting (i.e a color wheel, tints and shades, complimentary colors and how they interact etc). [esp because some “cheaper” paints will have other pigments mixed in. for example a cheaper red will not make a perfect purple when mixed with blue since it will likely have hints of yellow mixed into the red to boost the brightness.]
overall, have fun <3 baby steps. work tiny and simple in the beginning and the rest will come to you with patience and practice.