My vitamin D levels are high even in the winter, probably because I run outside year-round and eat loads of dairy. In the summer, I go out early in the morning and late in the afternoon most days, and don't bother with sunscreen if the UV index isn't high. If I'm going to be out all day in the sun, though (biking, hiking, kayaking etc.), I use the following for my face (I have rosacea so use mineral sunscreens which are supposed to be better for the environment anyway):
La Roche-Posay Anthelios Tinted Mineral Ultra-Light Fluid Broad Spectrum SPF 50, Face Sunscreen with Titanium Dioxide, Oil-Free, 1.7 Fl. Oz
It's about $33 for a small bottle, but it lasts me quite a while, up to a year even. It spreads easily in contrast to many other physical sunscreens, and the light tint means you don't get that white cast to your skin. It lasts me all day once I apply it.
For body coverage, I usually use a long-sleeved rashguard when I go kayaking, but I also like the following spray-on sunscreen when I'm not going to be able to avoid the sun during peak hours on the water:
Neutrogena Beach Defense Sunscreen Spray SPF 70 Water-Resistant Sunscreen Body Spray with Broad Spectrum SPF 50, PABA-Free, Oxybenzone-Free & Fast-Drying, Superior Sun Protection
This is about $10 a bottle and we go through it faster since we use it for our bodies and re-apply frequently if we're out all day.
I don't skimp on sunscreen; the best sunscreen is one that you're actually going to use and that's not going to irritate your skin.