I don't think I've ever bought any bags or containers for food storage, either in the freezer, the fridge, or otherwise; I re use old ones -
Oh, I use a butty box that I bought years ago, but that's not actually for storage
Plastic bags --
those used by supermarkets and other shops to put loose fruit & veg in
the inside bags from breakfast cereal packets
bags of frozen veg, etc
Bread bags
Containers of margarine, yogurt, potato salad & similar tubs
Containers from chilled ready meals don't usually have lids, just a plastic film; used as trays in the fridge for eggs, tomatoes, etc
Empty jam & coffee jars
Ice cream tubs
Wash them, label with a felt pen, usually a Sharpie, or sticky labels - I got a big packet from a discount store very cheaply, then Sellotape on top if it's for long term storage
You can wash plastic bags, turn them inside out as required, but it does take a couple of days to dry
Clothes pegs & elastic bands to seal the bags
Sometimes I make a big batch of stew and dispense it into single servings in plastic bags, then freeze it. When it's thawed, cut open the bag and throw it away
But note - some of these containers might have held sweet & carby foods, but that doesn't mean I buy them every day by any means
I'm sure you'll find more ideas if you Search t'Net & YouTube
Although not specifically for storage, Search t'Net & YT for BENTO BOX, which is a Japanese food box; besides the actual box there are ideas for taking your own lunch