Perhaps the simplest and least intimidating, but not necessarily the shortest, is 15 south to Barstow, 58 west to Bakersfield, and 99 north to Sacramento. Catch I-5 in Sacramento north to Redding. And pretty boring. All freeway excepting portions of 58. This is shorter than going all the way into LA and catching I5.
Or, 95 north from LV to Fallon (all 2 lanes) to Reno, to Sacramento (all 4 lanes on I80), not exactly direct, and of course, you will be driving through lots of high desert. I love the high desert and can drive it all day and love it, but not everyone's cup of tea. Lots of places on this route to dry camp, but limited numbers of improved RV parks/services.
Going up the difficulty scale (and maybe not recommended for first time out), 160 from LV to Death Valley, then 190 west from DV to 395, then 395 north to 88, 50 or 80, to cross the Sierra. Some serious grades leaving Death Valley to get to Lone Pine on 395.
Crossing the Sierra from 395, Highway 88 is two lanes, the least traffic of the three summit routes, but a year round highway and most scenic IMO. US 50, two lanes from Meyers to Riverton, then four lanes from Riverton to Sacramento. I80, less scenic, most traffic, all freeway from Reno to Sacramento. I would not use 50 (only because it is so busy and only two lanes over the hill), but wouldn't think twice about using 88 or 80 to summit.
You can also backtrack on 15 south to Barstow, then 58 west, then catch 395 north and choose from any of the open Sierra passes to get over the hill and catch 99 north. IMO, this is the most scenic option of the three, driving north on 395 with the Sierra Nevada Mountains giving you a backdrop to the west as you drive. Again, lots of dry camping areas on 395, and a fair number of improved RV parks. No real challenging grades on 15, 58 or 395. The only really grades would be 88 or 50, if chosen, and RVs traverse those highways year round.
From 395, you could also take Tioga Pass over the summit (if Tioga is open when you travel), go through Yosemite, then take 120 west to 99. Very scenic. Steep mountain grades. Two lanes. Probably not a good choice for first time out.
Coulter & Friends
2004 KSDP 3353/Cummins 5.9/Allison/Freightliner