Is it a good sign if after improving my diet my vit d level raised 5 points in 6 months? can my level be raised more without supplements?

Depends...: rather than an absolute number, where you moved on the laboratories scale is the key point. We are finding that a lot of people have low vitamin D and that goes along with a lot of minor ailments (probably at least somewhat BY COINCEDENCE.... people with poor diets might be poor, have bad dental care, smoke, etc. and have low vitamin D). Really decent sun exposure will increase vitamin D level.

Yes: Sun exposure is an easy, reliable way for most people to get vitamin D. Exposure of the hands, face, arms, and legs to sunlight two to three times a week for about one-fourth of the time it would take to develop a mild sunburn will cause the skin to produce enough vitamin D. The necessary exposure time varies with age, skin type, season, time of day, etc. It’s amazing how quickly adequate levels of vitamin D can be restored by sunlight. Just 6 days of casual sunlight exposure without sunscreen can make up for 49 days of no sunlight exposure. Body fat acts like a kind of storage battery for vitamin D. During periods of sunlight, vitamin D is stored in fatty fat and then released when sunlight is gone.

Supplements easiest: Realistically speaking, trying to raise your levels significantly with dairy and sun would be difficult. Supplementing vitamin D3 daily, 1000-2000 units, should do the trick.