Will my gerbils always be so skittish?

It's hard to say. With proper taming, most animals will warm up to you in time.

However, it sounds like you're not using a proper taming process. Don't feel bad! It's a common mistake.

Never chase your pet around the cage! It's very stressful to them and it bruises the trust. Instead, try putting something like a toilet paper roll or some other sort of tube into the cage and let them crawl into it on their own free will. Start out by lifting the roll for a few seconds to get them used to being picked up. After a day or two of this, you can try putting your hand at the opening of the roll and seeing if the gerbil will climb upon it on its own. I wouldn't recommend dumping them into your hands, but we can't confirm if that'll make any impact on the trust or not, and I wouldn't want to risk it.

Alternatively, try placing your open palm into the tank and waiting. Some animals will climb upon it and examine your hand. Don't inch toward them or lift your hand the first time - this will frighten them and cause them to fear your hands. After they've examined your hands a few times, you may try lifting them up slowly. Only do this for a few seconds at first, but build up every time. Eventually, you can take the animal out of the cage entirely and see how it reacts.

If it refuses to climb into your palm, entice it with treats. Most rodents adore a good treat, but rarely, they don't care for them. If they happen to not care for them, you'll just have to deal without and be particularly patient.

Some animals, especially ones that have been mishandled, will take longer to warm up to you. Be very patient, and love them regardless. Good luck with your pets.