First Custom PC

Have no idea where to start, I get a lot of mixed suggestions on what do, what to get and why. Thought I'd come here for more advice. Want a system that'll last a while and that I can upgrade parts when needed.

1. What is your budget? [€2650 - 3000(if needed)]

2. What will be the main purpose of the computer? [Gaming (Mainly single player games and mmos), 3D Modelling, Programming, Work]

3. Do you need a copy of Windows? [No]

4. Can you use any parts from an old computer? [Nope] (If possible state brand and model of the parts to ensure compatibility)

5. Do you need a monitor? [No, always have them]

5a. If yes, what size do you need. 

5b. If no, what resolution is your current monitor and do you plan to upgrade in the near future? [both 2550x1440] [No]

6. Do you need any of these peripherals? [No]

7. Are you willing to try overclocking? [No]

8. How can you pay? [Credit Card]

9. When are you purchasing? [1-3 months]

10. If you need help building it, where are you based? [I will try soloing this]

Thanks in advanced !