Get a desktop. Laptops will never be as fast (or cheap) as desktops. Just... don't get a gaming laptop.
http://pcpartpicker.com/list/rfwRKZ Inexpensive, but will probobly hit Beam at 60FPS 1080p on high-highest settings.
I'd definitely recommend something like an i5-6500 (like I have) over an i3-6100, as BeamNG uses 1 core per vehicle, and the more vehicles you want, you'll need more cores if you want smooth gameplay.
But the i3 has hyperthreading, which emulates 4 cores at no performance cost. And its 50-100 bucks cheaper. And that build I sent you is the build I'm going to build mid 2017, so if you end up building it, would you mind sending some benchmarks/FPSs? --- Post updated --- Sorry, forgot them quotes.
Hyperthreaded cores are nowhere near as good as actual cores for gaming. For some other things, sure, but from what I've seen even if it's more expensive an actual quad-core CPU will be better than a hyperthreaded dual-core. Some games will have performance differences but usually hyperthreaded cores only deliver 10-20% more performance at most, and imo it's better to just spend a little more and get real cores. Intel's cores are beefier than AMD ones which will increase performance in BeamNG. PC parts are always cheap around mid to late March when new stuff is coming out, that's when I built my PC. I'll send along some benchmarks and FPS results soon
I used BeamNG drive on my university laptop, the Asus N552VW-FY136T, a very good laptop despite gaming is not a priority for that notebook, it costed me 1100 Euros, i suggest you an Asus ROG, an MSI or an Alienware, the best gaming notebooks
Certainly laptops have many limitations and it is a needs based decision. My MSI Dominator has served me brilliantly for 3 years now and runs BeamNG to my complete satisfaction. If I had the space and lifestyle to accommodate a desktop it would be a 10 core 1080 SLI monster, believe me. My laptop is purposed as a 'desktop replacement' and it does it's job perfectly. Added a 1 TB SSD with room for still another. There are many valid reasons for people choosing a laptop over a desktop.
I can run 4 vehicles in ECUSA at 1080P before I start seeing lag. 5-6 cars on other maps depending on the map. My settings: AA on SSAO on FXAA on Mesh quality high Texture quality high Lighting quality high AF 4X Dynamic reflections all mid level Grass density 1 These settings suite me fine and I could actually lower some of them to increase vehicle counts without a bother. All screen shots I post are with these same settings and are completely satisfactory for a laptop in my opinion.
I did some bench-marking with my i7. Here it is: http://www.beamng.com/threads/performance-scaling-4-cars.21880/ Imagine hitting that performance hit with three cars instead of five. I'd recommend an i5 over an i3 for Beam.NG. Using hyperthreaded cores tank performance.