Never spend more than 2 crystals when crafting.
The available items level is determined by your equipments level, so you will replace your equipment too quickly to justify wasting more crystals.
Also, you can right click while hovering over the scrolling items when crafting to land it on what you want safely and give you a chance to inspect what the stats are. Then just left click on the "Stop Wheel" button to confirm the item, or click elsewhere to move the wheel again.
Lastly, if you don't see any items you want when crafting, you can refresh the page while the wheel is still spinning and you won't lose any crystals.
Very nice game, but it needs A LOT of work. Finished at 209 days with a score of 9,999,568.
To those who are saying the beginning is too hard, fill your peripheral with resources immediately and build as many troops as possible. Building a new resource gives you the same as amount as upgrading one, but it is much cheaper.