With a secured credit card, your monthly repayments are reported back to credit reference agencies, so provided you use your secured card responsibly (staying within your credit limit, making all repayments on time etc.) it’s likely to have a positive effect on your credit score. Using a credit card rather than a debit/prepaid card also gives you access to purchase protection under Section 75 of the Consumer Credit Act for items individually worth £100-£30,000.
Secured credit cards could be a step in the right direction, but only if you have the money to pay the deposit in the first place. Once you’ve become a master of your credit handling capabilities and begin to see improvements in your credit score, you may no longer need to be tethered to a card with a security deposit – meaning you can apply for an unsecured card.