Whenever i create a game, I grab some ideas and write them down.
But then i want to start, Thing is…
Do i make the hard things first? (This would be gameplay mechanics mostly.)
Or do i do the easy things first? (Such as making a gui.)
If i make easy things the hard ones come after and i want to give up.
But if i make the hard things i’m not even sure how much progress i’ll make.
Do the hard ones first, so you know that when you’re done and over with it the rest of the game development will just be easy.
I’m making an obby, and I done all the donations, checkpoints and stuff first. That was the hard part, then I moved to the easy part; making the obstacles.
Alright, Thanks, I’ll wait for some more responses to see what the majority thinks!
I also agree with @KFiesh you should do the hard parts
First because then you have a sense of achievement wich will motivate you to do the easy parts then your game will be done 
Always Start with the hard parts. I have a scientific reason to do so.
When you start a project your most likely motivated. If you do the easy one’s the more you work the less motivation you have. then when the hard ones will come you will give up. Thats why that if you do the hard one’s first everything else will be easy and you will have enough motivation to finish the game.
Thats it!! Keep it up man.
Thanks! I’ll do the hard part first then 
Do the core mechanics first. You want to build the base and then go off of that, add things later on that require those foundations already scripted. Don’t go by difficulty, go by how necessary it is first.