moving gantery CNC sturdiness

[RonVais]

well guys you are right i need to start designing before thinking about anything else so i started modeling and planing the project and some questions came up:

My main limitation is i dont have access to any milling machine or any metalworking precision tools.
And the base matirial i was thinking of was steel rectangle tubes (50*100mm with wall thickness 3.2mm) mainly cause it is massive and should vibrate less and it is can fit into my budget

And the first question that was on my mind is how to connect all the parts of the frame?
I think i will not be welding because i dont think i have the skills to make it precise enough
So the alternative is having the steel cut precisly at the store, connecting with bolts that way i have option to compencate most errors with shims and a file
(If you have any thoughts or tips for me it will be very helpfull)

The second thought i wanted to run by you is : i was thinking of geting the two ribs under the linear rails from thicker steel (3.2mm 50×100mm tube) and the other two ribs of the frame from thinner (40×40mm 1.5mm thick steel profile) below the first two ribs


By the way i was thinking to try and simulate the vibrations of the machine - the fundumental as i understand is 3.3khz for two flute at 10,000rpm
What would you emphasize on in the simulation?