Kids with autism often have poor proprioception and sometimes lax muscles in their forearms, both of which significantly effect the child's ability to write legibly. It is important to have them continue to practice, and free printable practice sheets can make a huge difference! I try to make my designs fun so that the child will be engaged, to save money on ink, I do recommend printing only one or two in color and using black and white copies (simply set the printer to grayscale) more frequently. I save the full color copies for rewards!
Some of the designs such as "Trace the falling stars" were designed so that the color would be so light, it should use fairly little ink- I know I can print a few hundred copies of that one with no problem- I have the HP Deskjet F4280, I used to have an Epson, the Epson ran through ink VERY quickly and was expensive to replace so please.... try one or two out and see if your child even likes them before you go too crazy!
Cutie was having fun helping me with a few of the designs, the "girl's writing practice" was tough- neither of us understand this princessy obsession that has taken over the US, the page is so girly, I nearly threw up on my keyboard!