The short answer
Start with the reformer if you want guidance and feedback. Start with the mat if you want the lowest-cost way to learn the basics. Neither is more correct: both train the same principles of breath, core control and alignment.
How the reformer differs from the mat
A reformer is a sliding carriage with springs, straps and a footbar. The springs add resistance when you need strength and support when you need help. On a mat, your body weight is the only load, so small errors in form are harder to feel.
That support is why many beginners feel steadier on a reformer, including people with stiff backs or sensitive knees. If you have an injury or a medical condition, ask your doctor before you start.
What to look for in a first class
Choose a class labelled for beginners, and check the class size. A smaller group means the instructor can watch you and correct your setup. At Jian Pilates, group classes are small and run for 50 minutes.
Where to try it in the Klang Valley
Jian Pilates teaches Beginner Reformer at Jaya One in Petaling Jaya and at Bukit Jalil in Kuala Lumpur. If you would rather learn one-to-one, a private session lets you go through the machine at your own pace.