You can gift more than that if you do it for long enough and have it as a regular amount. Its called normal expenditure out of income. We give my son a regular amount on a monthly basis that we increase with inflation each year. We've been doing it for the past 10yrs.
The key is making it regular and consistent, so not as one off chunks (unless they are frequent chunks) and keeping records. But it must be demonstrably excess income, so you can't impoverish yourself.
This is in addition to one off gifts.
https://www.gov.uk/hmrc-internal-manuals/inheritance-tax-manual/ihtm14241