So this is the best advice I have: Pick a goal that is achievable.
Don't put the pressure on yourself of creating the next Bone - http://www.boneville.com/comic/bone-issue-one-page-11/ - https://en.wikipedia.org/wiki/Bone_(comics)
or One Piece - https://en.wikipedia.org/wiki/One_Piece (just in case you haven't heard of it)
Just make something that you can be proud of or happy that you made and allow yourself to build from there.
Give yourself benchmarks and little victories to keep yourself motivated, Otherwise you'll end up too overwhelmed to make anything which literally everyone who has ever tried to make something has felt at one point or another.
I really think your Game / Thriller Idea is intriguing and could definitely merit a full graphic novel, but unless you've already got hundreds of pages under your belt it might be better to take that concept and turn it into a short story, like 20 pages in that universe with those characters, but instead of creating an endless epic tale, make a self contained story-line that has room to grow but gives you a finish line that you could get to within a few weeks.
This is usually how serialized comics and stories are done, one story arc at a time.
Here are some good comics for motivation and to keep this thought going:
https://zenpencils.com/comic/90-ira-glass-advice-for-beginners/
https://zenpencils.com/comic/119-john-green-make-gifts-for-people/
I like to think of writing and comics like running a marathon, I have had hundreds of false starts, ideas that didn't pan out, and embarrassing failures, among maybe 1 or 2 pieces of work I am proud of. Similarly you don't just decide you like running and run a marathon the next day, it takes thousands of hours of practices, short runs, jogs with friends, training specific techniques, and most importantly endurance to get to that level, but the big secret is after you've done something from start to finish it isn't scary anymore, it is a monster you've already beaten and you can do it again and again getting better each time.
Just keep your pencil moving, I hope this helps.