To figure out how much fabric to buy, you'll need to measure the length of the bodice and the length of the skirt. You can do a empire waist seam, natural waist seam, or even no seam at the waist. You'll need the front and back of the bodice, front and back of the skirt, and sleeves if you want them. (I'm only helping you figure out the lengths you need because most fabric is wide enough to accommodate circumference.)
Now when planning for the fabric of the skirt, you'll have to take into consideration the print and style you want. If you have a solid or all-over print, I would advise an a-line skirt. It's the most flattering, you get lots of movement without a lot of bulk where is gathered at the waist seam. An a-line skirt shape looks like this. It has a curve at the top and a curve at the bottom. You would take your skirt measurement and add extra to the top and bottom to give room for the curve.
If you want a striped dress, decide the style you want. If you have a flared skirt it'll throw off the stripes. If you have a straight skirt, you'll have more gathering at your waist or a skinnier skirt at the bottom.
Here are two examples of a straight skirt and flared skirt. On the skirt on the left all the stripes match on the side and the hem is a straight line that follows the stripes. On the skirt on the right the hem curves and the stripes get cut off.
If you want to do a full-circle skirt you'll need lots and lots of fabric. This is an example of a full circle maxi skirt. See how the stripes look like they curve up then down?
This is one way to lay it out. You might have to cut it out in two pieces to get the length you want.
It you want a chevron effect on your dress you'll have to cut out your pieces on the bias, like this. You have to match up where the stripes hit the pattern, look at the circles. Make sure that the stripes will meet at a point going up or down. (I didn't draw this to show how save fabric, just how to lay out the pattern.)
Once you decide what your style of dress will be, draw out how it will be to see how much fabric it will take. Like this. A flared skirt style on the left and a straight skirt style on the right.
If it is too overwhelming to make up a pattern without detailed instructions, don't worry, tomorrow I'll share lots of maxi dress tutorials you can use so that you can still make your own maxi dress!
Besides the dresses I've already showed you here are some other dresses I am inspired by.
Love these sleeved versions.
You could just sew a maxi skirt onto a shirt.
What dresses inspire you?