The amount of salary or compensation of officers and employees shall be provided for in the budget, which shall provide, as nearly as conditions allow, uniform compensation for like services. An increase in compensation of any officer or employee in the administrative service, within the limits provided for the class, may be granted at any time by the mayor or other appointed authority upon the basis of efficiency and seniority. All appointive officers and employees of the city shall hold their office and employment at the pleasure of the city commission.