Each plant needs a specific soil composition of suitable acidity. For example, among flowering plants, gardenia and camellia love acidic soil, slightly acidic - Fuchsia, Anthurium, Jasmine, Spathiphyllum, alkaline - Adenium, neutral - Aphelandra, Pelargonium, Rose and others. Over time, any, even ordinary soil, in conditions of indoor maintenance and home care of plants, begins to change its properties due to applied fertilizers or hard water. That is why each plant needs to change the soil at least once every two years, and renew it annually - in the spring. Particularly caring owners additionally measure the acidity of the soil in which their flowers grow.
Concerning the pot: when transplanting, it is recommended to choose a pot with diameter being only 2-6 cm larger than the previous one (depending on how much time has passed since the last transplant and how the plant has grown during this period). The main condition is that after transplanting a plant into a new pot, its roots should be placed there freely, maintaining a certain distance to the walls of the container. This distance should not be too large - otherwise the roots of the flower can grow, and it will spend the bulk of the reserves on their development, and not on flowering.