Many people learn how to sew using commercial patterns. It's a good place to start, but if you have made things from commercial patterns you know that the fit is never quite right and things don't always sit as nicely as apparel you can buy. If you still want custom fit apparel that is exactly how you want it, you must learn how to pattern your own clothes.
Having the right tools for making (or modifying patterns you purchase) is a super important place to start. Luckily, most tools are not expensive and are easy to get.
Here's the quick list. I'll go into detail for each tool after the list.
1) Large scale paper ( Blick White Utility Paper Roll )
2) Clear Gridded Ruler (I recommend these, 18" x 2" is a good starting size: 8ths Graph Beveled Ruler )
3) Flexible Design Rule
4) Hip/Arm Curve (Styling Design Ruler) (Visit CreateForLess and search for "Styling Design 4 in 1")
5) Pencil and a good Eraser
6) Large pins
7) Cork panels
8) Flexible Measuring Tape
9) Basic sewing book
Large Scale Paper
Such as butcher paper (18" wide on long rolls), banner paper (18" wide roll and often sold with school/office supplies), patterning paper (36"-48" wide, sold by stores that sell patterning tools or cater to high end sewing and tailoring).
18" wide paper is wide enough for many personal patterning projects. You may need to tape pieces together to accommodate patterns with a lot of fullness but it is not unmanageable. If you are serious about patterning, buying a roll of 36"-48" wide paper is absolutely worth the investment but it is expensive and very heavy. You will want a designated patterning area to store and work with your roll of patterning paper because you will not want to move it around.
Clear Gridded Ruler
These rulers are pretty easy to find at most craft stores (check with graphic design tools if you don't find them with sewing notions). The most common size seems to be 18"x2" which is a great size to start with. This style of ruler comes in many sizes and shapes. The variety comes in handy and the more you pattern (and figure out who you are as a designer) you will want to grow your collection by buying rulers to fulfill certain needs and uses. The 12"x1" ruler is extremely useful when adding seam allowances to small pieces or sharp curves.
Clear quilting rulers that are 24" - 36" long can also be helpful. However, they typically don't have consistent markings throughout the ruler like the gridded rulers do. They aren't the best choice for your main patterning rulers but they do come in handy for things like center front/back lines, sleeves, and skirt lengths.
Flexible Design Rule (Flexible Ruler)
This rule can be curved into specific shapes and you use this to measure curved lines. They are often placed with quilting notions in fabric stores and, like gridded rulers, can also be found with graphic design tools. For most versatile use, make sure you get one that has a built in ruler.
These are becoming easier to find in sewing stores. This tool is designed to give you the best smooth, consistent hip and armscye curves with little effort. You don't need this tool but my does it make patterning easier!
Pencil and a good Eraser
You want to use pencil when patterning so lines can be erased and re-drawn. Mechanical pencils are a better option because of their incredibly consistent line width. A good eraser is an imperative also. Most of the lines you draw when you pattern will be re-drawn or altered at some point during the patterning process. You will want a good eraser to cleanly remove old lines leaving no marks behind that could confuse you later on.
Large pins come in handy when patterning (especially when use with cork panels). They are used to secure overlapped layers of paper when you check to make sure your lines flow well as well as to transfer marks from one layer of paper to another. They are great for when you move or add fullness (darts, flares, etc).
Most large stores that sell office/school supplies sell cork panels. They are meant to be used as bulletin boards without frames but I found them to be a great work surface when you need to rotate your pattern pieces to move darts or add fullness (pin and pivot). The cork panels in the image above are 12" squares and are typically sold in packs of 4. When laid out on a table, they can be a great surface to work on when you need to pin into something or transfer marks from a pattern to fabric. I have found cork panels are useful in so many aspects of sewing.
Flexible Measuring Tape
When making patterns - whether they are custom fit or you are working with a generic block/sloper - you will need to measure yourself to determine the proper sizing, proper proportions, or ideal placement of certain aspects and details. Keeping a flexible measuring tape handy will be an asset.
Basic Sewing Book
When you make your own patterns, you decide all the details. You choose the method for inserting a zipper or adding a placket for buttons, what type of pocket you want, how you want the seams finished, if you will use facings or line the whole garment, and, well, everything! When you are making your decisions on how you want to finish your garment, it is super helpful to have a good book of sewing techniques to refer to. Some techniques require different seam allowances (I always leave a 1" seam allowance when placing a lapped zipper) or additional pieces (like making welt pockets).
Patterning Book (not pictured)
There are several very good books for creating your own sewing patterns. There are a few different ways to approach patterning and you'll have to figure out which techniques (and authors) are best for your body type and working style. I will give you a tip - if you are serious about making your own patterns don't waste your money on the patterning books sold in craft stores. I don't own a good patterning book that cost less than $40 and the most comprehensive patterning book I own is +$80 (and worth every penny).