@Geeta,
Ruby should be worn in Ring finger, Yellow Sapphire in Index Finger and Blue Sapphire in Middle finger. So you can manage these three in one hand. BUT, there is no Sun sign or Moon sign in which these three related planets are Karakas (planet ruling the benefic houses such as 4, 5, 9, 10).
For instance if your ruling sign is Leo then Blue Sapphire become Markesh for you. But if your zodiac sign is Libra then Yellow Sapphire becomes Markesh (planet ruling the malefic houses such as 6, 8, 12 or even 2). Hence, by no means one should wear all these three gemstones at the same time.
For the right gemstone combinations please kindly submit your birth details.
Best Wishes!