Adobe Illustrator is the best option because graphics are vectors, meaning you can size and resize your images without making them pixelated. You can create poster sized images or cake toppers with the same graphic and the quality of the graphic won't be affected.
The great thing about printables for personal use is that you don't need to have a fancy printer or pay a printing company a fortune. Simply print graphics at home with an inkjet or color laser printer. You can find a printer for as little as $60 or upwards of $2000. Don't think you need an expensive printer to create incredible graphics. A printer in the $100 range should work fine.