Measure the kiln size so you do not purchase pieces that will not fit. Subtract an inch from dimensions to allow space for the piece.
Items that fit in the hand are in demand where large wall mount plates and tiles are a tough sell. Walk through unlikely stores. Back to school sales often includes ceramic wares that can be painted. A local grocery store may have ceramic dishes that are affordable. If you want multiple matching pieces consider ordering on-line. Shipping to the store is often free. Imperfections in less expensive china wares provide unique opportunities of incorporating in a design.
Lowe's and some Home Depot stores have white and colored ceramic tiles priced for beginners.
Low-fire bisque ware (unglazed) is available at most ceramic stores and often priced for beginners. Low-fire bisqueware must be glazed to produce a surface ready for china paint. I apply 3 - 4 coats of Amaco clear gloss glaze (LG 10) with a foam brush allowing time for drying between applications. Fire at 1,940 F.
Dollar tree stores have variety of ceramic cups, saucers, plates, bowls and boxes. They often have glazing or kiln problems. A Dremel grinder with ceramic grinding wheel will smooth imperfections or a dab of china paint may fix a flaw.
Some Walmart stores have a limited supply of Mayfair ceramic cups, bowls and plates for about a dollar. They also have white ceramic dinnerware set from Mayfair (32 pieces and 6 place sets) for less than $30. I have found early morning the best time to check shelves.
Thrift stores have used ceramic items that may be painted but often the same price as new so watch for bargains. Some thrift stores have half off days and sometimes you can bargain the price down.
Metal items are paintable.
Food stains found on many used items are easy to remove by firing with your other painted pieces before painting.
Scratches and knife marks of used ware may be removed by applying 1-2 coats of Amaco clear gloss glaze (LG 10) with a foam brush allowing time for drying between applications. Fire at 1,940 F.
In 2018, I took a leap into the ceramics world and started to make pieces for china painting. They are either glazed white or clear. Sometimes I will glaze darker colors leaving a white face for painting.