People sometimes say, "I fancy that". This means they want it.
For example, if a man sees a nice car, he might say "I fancy one of those".
This means he would like a car just like the one he sees.
When people say, "that suits my fancy", they mean that what they see matches with what they want.
If a woman sees a beautiful diamond ring in a shop window, she might point to it and tell her husband, "that one suits my fancy". He then knows that ring is the one she desires.
Hope this helps