Are you using or planning to use GRAMPS?

I use Wikitree to document my tree. GRAMPS was a consideration but trying to share with older relatives was going to be an issue for me that way. I do keep a local GEDCOM copy though. Yes I do feel disgusted the LDS created the format every time I save a backup. Gedcom files can be used with basically everything if you weren't aware.

The biggest pitfall I've seen is trusting other people's work. At all. You might stumble upon what looks like a full family tree of your relatives and start adding people to yours and get all excited about this treasure of information you've found. You'll realize later it's probably so big because the person spent a while on Ancestry.com just randomly accepting any "match" and it isn't really that accurate.

There's absolutely nothing wrong with perusing the trove of data on acenstry.com, and there's good trees around from there. Just verify.

The second biggest pitfall is similar, start by not trusting family stories. In my family I always grew up hearing we were related to the people who built the white house, and had Native American blood (an especially common story in America which I could write for ages on) in us, and were related to a famous poet. Turns out none of that was true and until I realized that I spent hours chasing down random paths trying to prove those things I supposedly knew. Turns out we just had someone who's name was "White", there may be an ancestor who's last name was "Whitehouse", the poet just happened to have the same last name, and for us a part of the family was in the KKK and disappointed a different family member had married a person of color and to cover it up they claimed the dark skin was native american.

And you mention your grandma made her own cards?

Grandma made mostly greeting cards. Every birthday and christmas was a custom card from her. I wish I had thought when I was younger to keep more of them or at least a picture of some of them. She had boxes and boxes of stamps and different textured paper and strips of fabric and things. Each one was always hand made with care.

I have another hobby with fountain pens and trading postcards around the world and know I could have put at least some of it to use.