Complete Beginner requiring advice!

[JAZZCNC]

Do not even think about using unsupported rails or an angry Yorkshireman will beat you with them.

So that's what you say about me when I'm not around.!! . . But You miss judge me D.C I'm not Angry am just a miserable Twat. .

He's correct thou you would deserve a beating if you buy UN-supported round rails.

Given the relatively low work load and accuracy required for just cutting wood and If this machine is just for hobby use then supported round rail will be your best option for a few reasons.
1st they are much cheaper but more so they are much more forgiving than Profiled rails regards build tolerances.? Profiled linear rails are much better regards durability and tolerances but they also need much tighter tolerances regards mounting surfaces etc being very unforgiving of poor workmanship. For Hobby wood cutting use they are bit OTT, esp if your on a budget.

With the Design and materials then Again D.C is correct keep the Z axis extension to a minimum and if its within your skill range then using Steel box section is much cheaper and very strong.
To add to this regards design then try to avoid high gantry sides. My preferred way is not to have any gantry so to speak and mount the Gantry direct onto the rail bearings. This means designing the frame so it raises the rail mounting surfaces but unfortunately it mostly suits using Twin ball-screws on the long X axis. It could be made to use a single centre driven ball-screw but just not has clean a design and weaker.
This twin screw design is very very strong and ridge which helps eliminate Twist, resonance and flex which is the enemy and gives poor finish etc.!! DONT under estimate the forces required when cutting, Even wood.!! Weak gantry and Z axis will result in poor cut finish.
(Will attach render of wood cutting design to give an idea of what I mean regards gantry on rails)

ONLY use 10mm pitch or higher ball-screws for wood use, 5mm will be too slow. 16mm Diameter will be fine, 20mm max.
Don't use 25mm which are commonly available has they are too big for machine this size and require large motors etc.

Motors best suited will be 3 or 4Nm Nema 23 don't use nema 34 has again they are unsuited to machine this size and would actually give less performance not more has is commonly mistaken.

To get the best from steppers then Voltage is very important. Common mistake leading to poor performance is using too low voltage PSU. Lots of motor/driver kits you see often include under sized PSU mainly because they use off the shelf Linear PSU, it also suits the supplier because they are very comfortably within the Drives voltage threshold so less chance blown drives.
With Wood machine then speed is important so sizing the PSU correct becomes important this Sizing also impacts the drives you use. Won't go into all the Crap of why and how etc it's all repeated here on the forum if you want to search but I will tell you thru experience cutting out the crap buy 3.1Nm motors and run them between 65-70Vdc using 70-80V drives.

This leads nicely to Drives and Electronics.!! . . . If you can afford Digital drives then buy them the are worth the investment.
DON'T Skimp on the drives, PSU and to some extent the BOB (Brake out board) they are the Life force of the machine and the sizes I suggested will transfer to future machine giving some future proofing.

The control box and wiring are often skimped on by using unshielded wire and cheap switches etc but again this is false saving and will lead to hair pulling and head scratching chasing problems it also works out more expensive in the long run.

Don't be tempted to run out an buy the Drives motors etc first has lots do has your just wasting warranty and chances are it will be months before your anywhere near needing them. Same goes for WC spindles ETC wait until your ready for them.

Best advice is Design machine then show and Ask. Don't be afraid to ask or think outside the Box just don't try to do it on the cheap it never works.!!
Don't rush out and buy anything without very carefully checking you understand exactly what it does and if it fits your needs and again don't be afraid to ask.!
Unfortunately I can't be around has much these days with today being a rare morning to my self to catch up on things so if you do have any questions specific to me I may not answer straight away.

Good luck and happy building.!