Shovel Smith/Guides

Overview
Shovel Smith is much easier to level with a high level lumberjack/blacksmith - it is possible to buy the resources for most shovels but it is not easy to recover costs at low levels by sales/smashing. A L40 miner/lumberjack and a nearly empty bank (for low withdrawl fees, or alternatively a house) can make levelling Shovel Smith reasonably painless. Note that most ingredients are fairly heavy in bulk, so a powerful Bworky may also be helpful.

On resource efficiency
More complex crafts may give more experience, but they do not always give more per unit material than the simpler crafts. For the least expensive levelling, you will want to calculate the XP given per craft over the number and cost of resources available - often this will end up being a recipe much easier than the most complex you can craft (although making things too much simpler than what you're capable of will give no experience).

L1-40
For levels 1 through 20, you'll be best off making Small Twiggy Shovels (2 ash, 1 wood). They won't sell well, so you will probably be best off smashing them for runes (which you will use to level shovelmagus, once you get there). This recipe is very efficient, each ingredient weighing 15 pods and being among the easiest to acquire in the game (high level miners may find bronze easier to acqure in bulk than iron). It is possible to continue crafting these up to level 59 while still getting experience, and if you want maximal ease hitting level 60, this is not a bad idea. It is possible to do better though.

L40+
At this level you should consider switching to Small Mechba Shovel (4 iron, 4 bronze, 1 tin, 2 cherry) if you have a lumberjack that can cut cherry and a miner that can exract tin. It has a significantly better (about 1.3 times) experience-efficiency than small twiggy shovels, and by this point your miner is probably beginning to acquire a stockpile of bronze (the most plentiful ore in the game). You can begin crafting this recipe earlier, but the failure rate makes it less efficient than twiggy shovels which by now are a sure bet. Do not sell or smash your small mechba shovels though - you will use them for your next recipe. Continue making (and banking) them until post-shovelmagus levels.

L65
Get shovelmagus and level it so you'll have even more carrying capacity.

L75+
At this point your failure rate for 5 ingredient recipes should be very low. You will want to begin taking your Small Mechba Shovels out of the bank and making Great Mechba Shovels out of them (2 bronze, 2 iron, 1 cherry, 1 tin, 1 small mechba shovel). Both recipes should give experience up until level 100, and you can either sell (maged?) your Great Shovels or smash them to get runes to level shovelmagus.