Glad to see you're thinking the right way, too many people run right for the $$$ profe$$ionals and end up with $3000 worth of work that you might not have needed done. We just added gutters and drain tile to the 40 year old home we purchased last december. Had some water come up through the cracks with the spring melt. After fitting the "eavestroughs" as they're referred to here, we put the downspouts into 4" drain tile and routed this to empty about 15' away from the house in a small swale in the front yard.
To determine grade, you want to measure how many inches of drop does the land make for every foot away from the foundation. Can be simply done with a string level, two stakes and some twine. For the best drainage I think the rule is at least 4" drop for every 1 foot of distance from the foundation. Hope this helps.