Check the bobbin on your older machine. Is it in properly? When I started sewing, I missed that a few times. It made the tension funky. Once I got the bobbin seated correctly and "threaded" all was well. I would encourage you to use the machine you have during the learning process. In the meantime you can save up for a fancier machine and discover exactly what you need.
You're going to have fun no matter which route you take! Start clearing closets for your fabric stash! LOL!