People might assume that sure, but you can also always add more context and clarify if you want. It's always up to you what you want to share about yourself. There's also a lot of overlap between transfem experiences and other groups, it's not like one group has a monopoly on everything they experience. Plenty of cis women wear thigh highs, for example, and some cis men even.
The trans flag is cute! i like it a bunch too.
Hi!
Do you have a relative or friend looking to get rid of theirs? They might be happy to show you a thing or two while handing it over, and it's hard to beat free!
If that's not an option, charity/thrift shops or estate sales are great for finding older, inexpensive machines that are often in surprisingly good shape. Keep an eye out for major brands like Singer, Babylock, Husqvarna, etc.
If you're not sure about one, skip it, but if you find one you like, take it down to a sewing repair shop and they should be able to give it a good look and recommend anything it needs as well as show you the basics. If you don't have a repair shop near you and you're comfortable putting photos of the machine online, places like this are handy. Happy sewing!