I see many people, me included, on the forum using the skill tree calculator from https://bl3skills.com, which I think it is great. Unfortunately I think that it shows the level wrong. Based on the gameplay we have seen you will get your first skill point at level 3. Unlike the other Borderlands games you do not have to invest a skill point in the action skill first. This means that you can invest 48 skill points in the trees at level 50. As the skill tree calculator is set up now you only invest 47 points when it says level 50, meaning that almost all the builds on here is missing 1 point.
Hope you find this information helpful! I also want to say that I still love the mentioned skill tree calculator, many thanks to the creator!