Expense - maybe, but you need to consider this as a hobby.

Used sewing machines can be cheap. I have bought several at thrift shops for prices around $15. I was picky, and waited for the deals where there was a good looking machine (generally) and it had a box of attachment goodies.

My most recent purchase was $15.88 for an old used Singer 328k made in the 1950's or 1960's. This one was frozen up from sitting unused for a long time, and the lubrication had literally solidified. P Blaster, Tri-Flow or BreakFree will loosen and lubricate. WD40 is strongly disrecommended for sewing machines as over time it dries to a varnish like nearly glue.

I have read about repair of these machines ( as a hobby) and this worked out to be a fine machine which just needed a little work.

A Cleaning, Oiling and Adjustment (COA) will typically run $30 to $50 in most areas, but maybe you can get on the phone and get this info for your area.

Many people are quite happy with a WalMart Brother or Singer NEW sewing machine for about $100. Mostly, you will use a straight stitch and basic zig-zag now and then. You literally have no need for 128 fancy stitches and embroidery designs at your finger tips. Just look at gear that you have to tell you this. You want a little quality in the machine, so stay away from the real dirt cheap things.

You will want some cutting instruments, and it is often suggested that you buy quality scissors and/or rotary cutters (and cutting board). There are a number of small tools you may find you want.

needles, thread, thread snippers for use at the machine, pins (get the ones with beads on the end as you can find them easier when you drop them, and stick them in easier),

tapes, webbing, buckles, zippers,

Fabrics, insulation,

There are some excellent books on making outdoor gear, but mostly these date from the 1970's and 1980's. You can borrow these on interlibrary loan, for free. Copy out the pages you need or want. Also, from the library, you may be able to get video tapes or DVD's on sewing topics. Same for books on sewing machine repair. Used bookstores online are worth it.

Stuff sacks are common first projects, and you can often find instructions online.

You might be well served to buy a kit from somebody with instructions and illustrations as a next project, or you could just "wing it" as some are inclined to do. Kits available include quilts, packs, ponchos, parkas, ... but nothing yet like the booming industry in kits of the 1970's.

Reread the MYOG groups. They are full of interesting stuff on the major backpacking forums.

It won't be long till you can translate your dreams into gear.

In the 1970's I decided not to sew stuff. I regret that decision now.

Jim