I remember my very first sweater very well. I still have it somewhere, tucked away in a box. And since it was made from very low-quality acrylic, it will probably outlast time itself. I found the pattern in the beginner knitter book I used to teach myself how to knit back during a terrible snow storm that closed the university for a week. It was a garter stitch cardigan, and the yarn was a country blue color. Not only can that sweater probably stand up on its own, but also lacked any shaping and could fit at least two people.
But darn it, I made it.
I still have the second sweater I made. Also acrylic, but an oatmeal tweed this time. This one was a pullover with a beautiful cable pattern up the front. The sleeves are way too long and unintentionally bell shaped, and the body is a bit too snug to say the least. The same goes for the third sweater I made. Also a cabled pullover, also really long sleeves, but with a wool/acrylic blend, so it was more comfortable to work with and definitely softer and nicer to wear. Except I don't like to wear crop sweaters (I hadn't quite figured out sizing and measuring when I made it).
I love making sweaters. I really do. There's just something magical about being able to cover a larger part of the bod with something I made myself (when I was younger I desperately wanted to make my own pajamas. I saved my money and bought some beautiful linen from the fabric store. Mom helped with the pattern. I still have that pair of pajamas carefully packed away as a reminder). And once I figured out how to knit and crochet garments, sweaters became one of my favorite things to make. (Honestly, I love it all, but if you know me, you know that my true love in fiber is lace. I ADORE lace, and there are few things that give me as much joy as making an intricately lacy shawl, but I digress).
Sweaters can be intimidating, though, particularly if you aren't so sure about sizing or seaming or making a larger project that does require a rather substantial commitment in terms of materials and time.
So, here is my advice:
If you are going to make a sweater for yourself, take your measurements. Then take them, again. And, be brutally honest about your measurements. I get it; writing down your exact measurements without fudging on where the tape measure falls can be... uncomfortable. But trust me, the more honest you are about your sizing, the easier it will be to make a sweater. That means measure everything--the circumference of your head so you know how large the neck opening needs to be; your chest, your natural waist, your hips, the circumference of your arms (because then you know how wide to make your armholes and sleeves), the length of your torso, the length of your arms...
Choose your size based on the pattern notes about ease and bust circumference. Ease is either positive or negative. Positive ease means that the garment is meant to be a little looser. Negative ease means it's meant to be fitted. You cannot go by "oh, I usually wear a Medium when I buy clothes at the store." Commercially produced garments are NOT sized the same way handmade garments are sized. So, sure, maybe you normally wear a Small, but you might need to make what would correspond to a medium in a handmade or you might need to make an extra small depending on ease and chest circumference.
Buy an extra skein of yarn if you can. This way if you make a mistake or you find your gauge is off or you want to make the torso longer, you have the extra yarn to do so.
Don't be afraid to change the number of inches on sleeves or bodies of handmade garments. I have a longer torso than you'd think I do, so while a lot of sweater patterns will have you end the body of the sweater at 14 or 15" from the bottom of the armhole, I need to add another inch or two. Sometimes three. This is why you need accurate measurements. Not only will it help you know how long you need to make your garment but also whether or not you need more length before or after any waist shaping.
Remember that sweaters are just handmade projects like the smaller ones you've already made. Yes, they take a bit longer to complete, but it's just one stitch at a time.
Always keep your first sweater. And maybe your second. Heck, keep your third, too. Even if they don't fit. Even if you decide after the fact that while that purple was really pretty, it makes you look like a giant eggplant when you put it on. Keep it. Trust me.
It's okay to mess up because you're just learning.
And, I've already posted this link on social, but here's a great first sweater pattern if you're looking for one. It's the Harvest cardigan by TinCanKnits.