It's preferably better if you complete the Save the saloon part 1 and 2 before starting to actually level up as a fresh new account that needs to catch up with others. The only quests you do are the ones that give you free premium(except if you will purchase nuggets).You won't do any quests after this so focus on doing 15s jobs , it's better to add all your skills on Construction and Strength as most jobs with high exp need construction, for example you will start doing 15s in the spot that Lay Railroad Tracks , Build Train Station , Build Windmill etc , there are 4 earl jobs with high exp you can do from level 15 if you have everything on Construction and because of the free 8 skills from Education question. With the bonds you accumulated from the previous quests + the Pony Express quest you should have around 200 bonds , you can buy soap water for this so you can continue doing the 4 jobs 3-4 times. After this you will be around 22-25 level and more jobs will start unlocking because of construction skill but not all of them. You can continue doing 15s jobs on jobs like Harvest Potatoes, Feed the animals , Hunt coyotes, you will eventually get to 30 level , try to buy clothes that give you construction and leadership and you will be able to work in Construct a ranch house , Construct manor-house, Build Palisades, Construct a casino and Construct a mission. At first you will be able to do only 3 with the proper clothes but eventually at around level 40-45 you will be able to work all 5 jobs. From there you just spam 15s , it's also good if the jobs are silver, just search for one of the jobs in the map and cycle through the entire map to find a silver and stay there. Though you will need soap water or chewing tobacco to help you do 15s consistently and efficiently so you either spent nuggets and buy more soap water or take a break and farm products for chewing tobacco and find someone to craft it for you.
Conclusion: The fastest way is to level up is by doing 15s BUT it's expensive.
Conclusion 2: You need nuggets to be more efficient with your level ups and to be fast if that's what you want.
Conclusion 3: You can also level up with quests and PVP or build a church since very early but it's very time consuming.
Conclusion 4: Do whatever fits you better and ask yourself, is it really worth it?