You will need to finger tame him, and teach him the up command. Cockatiels are not great talkers, but can learn a few words and phrases. Some cockatiels are better talkers than others. If you can't afford a good size cage you can't afford a cockatiel. The wires should be a thick wire and run horizontally.
Cockatiels enjoy climbing up their cage.
Any bigger poses a safety risk. Their little heads can get stuck. Cockatiels need light, but don't put the cage in direct sunlight. If no light is available from natural lighting, supply a full-spectrum artificial light. This lighting is necessary for the bird to utilize vitamin D. Make sure the cage is in a well-ventilated area.