Look at the size of time required for you in ordering your wedding event cake.
To prepare the cake tin for baking, lay it onto a sheet of baking parchment and draw around the base, then cut out the circle. Cut a long strip of parchment a little taller than your tin. Fold over one long edge of this and cut slits every inch or so. Grease the tin and line the sides with the long strip, laying the flaps on the bottom of the tin. Cover the bottom with the circle. Once fully lined, do this all over again. Double lining the tin will prevent leakage, and give a little extra insulation to the cake.
Once you have your smooth surface you can take care of any flaws that are left. Marks and cracks in the icing can be hidden by taking a small ball of icing, dipping it in some cornflour or icing sugar, and rubbing it over the problem area. The icing sugar will fill the crack and blend it into the surface, smoothing it out. Other marks such as cake smears or food colouring can often be removed by brushing on a little clear alcohol, such as vodka, and then rubbing lightly with some kitchen towel. Once the liqour has dried smooth out the surface again.
Take a 30 gauge wire, dip it in edible glue, and carefully insert this into the raised ridge. Gently pinch the edges of the petal to give them a little realistic frill. If you have a petal veiner, lay the petal in the venier and press down firmly. This will give the petal veins and contours to make it more realistic, This can also be acheived with some patience and a thin modellling tool.
You should use a recipe specifically designed to be a wedding cake as it will ensure that it is sturdy enough and that it makes the right amount of batter and icing. For a three-tier cake, you need to make three cakes of 12", 9" and 6", as well as a massive amount of icing. Most three-tier cake recipes have a step-by-step schedule for when you will need to bake and assemble each part.