If you want to say "I'd like to buy your equipment"--- “我想買你的設備” or “我想購買你的設備” is both right.

"我想購你的設備" You can say it this way but it will be more oral to say "我想买你的设备"

im interested in your equipment, pls send price list to us. ----->我对你们公司的设备感兴趣，请提供价格表。 it just express u r interested it. however, u r not very sure if u will buy equipment from that company i want to place an order of that equipment to ur company. ----->我要购买你的设备 it means u r very sure(100%) u will buy equipment from this company