There are lots of bottles on the market and some are much more expensive than others but there’s no evidence that more expensive bottles are needed. In particular, if a baby exhibits colic or reflux symptoms, rather than changing to anti-colic bottles, families can try smaller, more frequent feeds using a responsive bottle feeding technique; this can work well with cheaper unbranded bottles.
Safe, cost-effective options for sterilising bottles without equipment are cold water sterilising, using sterilising tablets, or using a pan of boiling water. See this NHS – YouTube video for a step by step guide and options that suit your needs.
For help to buy formula milk, take a look at Healthy Start Scheme to see if you are eligible for financial support.