Lidl is very good for houseplans especially if you get them within a day or two of being delivered.
For indoor pots you can be quite creative. If you think about it you need something to hold the plant and soil then an outer container to catch excess water. Waste plastic bins, hessian bags, rope bins, decorated storage boxes, charity shop for big decorated ceramic serving dishes, vases, metal mixing bowls, baked bean can, sma type baby milk tin or giant sized coffee tin. It very much depends on your taste but Pinterest can help you work that out if the choice seams too wide.
I like to put a few broken crocks or stones in the bottom of a pot below the houseplant so excess water free drains and water in the bottom creates a humid environment without soggy roots.
Ikea do some lovely pebbles, small stones and ceramic balls. I like big glass bowls (so you can see the pebbles through the glass but not the plastic pot) or ceramic pots lines with these then the plastic pot or several plants in plastic pots, then fill the remaining space and cover the soil with the pebbles/ stones/ ceramic balls.
Plants in my house tend to do best planted in small groups as I need to water less in bigger containers.