It's an addicting hole to fall down, that's for sure. Start simple... your parents. Add their parents and any siblings your parents had. Then add your grandparents' parents and so on. Just make sure to verify each and every source before adding. My early trees are rife with inaccuracies because I just linked someone else's error-riddled trees with mine without checking their sources. Now I know better.
There are 3 main sites I recommend... I use all 3 regularly, as they each have things the others don't.
Ancestry
pros - LOTS of resources, especially US-based. Main site used in US, so a lot of people on the DNA side. Their tree function is easier to use than other places, and where you should build your main tree, IMO.
cons - $$$$$$, and can't upload other company's DNA test results.
Family Search
pros - free, has a lot of the same info as Ancestry
cons - not especially user-friendly, & the family tree isn't just yours, but a world-wide community tree. That means that someone else can come along and change info on your entries. This can sometimes be good, but it can also sometimes be bad.
My Heritage
pros - what Ancestry is to Americans, My Heritage is for Europeans... tons of European-based resources, though they do have a lot of North American resources, too. Can upload DNA results from other companies into theirs.
cons - $$$$$$. Not super search-friendly. Their tree function is also a little clunky.
An important source that's readily available to you, and is free, are the US Censuses. You can glean so much information off of them, though I need to note that ages, dates, and name spellings aren't always accurate, but such things weren't as important then as they are now. They're on Family Search. The most recent one is from 1950, so depending on when your parents were born, they might be in there.
If you decide to do a DNA test, I recommend Ancestry to start. Once you have the results, you can then upload them to My Heritage to see if there are any hits. It's a two-for-one deal. But Ancestry doesn't allow another company's tests to be uploaded, so that's why I suggest Ancestry's test over another... more for the money.