It’s not all about the beautiful party that you are planning or have been invited for but there is also something good about getting to thirty. You should point out to the person in your 30th birthday phrase that there is so much to learn about life from here since he/she is leaving the young world which is full of dreams and into the adult and serious world.

As a motivational or inspirational message, you could put a phrase that tells the person what a promising whole life there is in front of him which should give reason to mark a certain period in life. 30th birthday phrases could also revolve around the reasons why the person should be happy to be leaving the more youthful period of life and moving on to another life that has so much to offer.
You don’t want to offend the person but a funny little quote could do wonders for the person at this inspiring age. For an invitation, its time to show people how mature you are now with some use of witty sayings and quotes that even those who have seen you grow will surely know you are someone mature now.