How much does does it cost to renovate a HDB resale 4rm flat?

We just purchase a 4rm resale apartment in the east of Singapore. As we are newbie, pls advise us what kind of basic renovation usually required to be done and estimate cost? We need to set a budget but we do not know what price is realistic and what is not? It is simplfied 4rm flat (84sm), ceramic floor tiles, alum window & grilles, rework top c/w sink in kitchen and decorative timber door for all bedrm.