Tips from someone who reached water a few times. These tips are purely for reaching water, and have little to do with achievements for the most part:
1. Prioritize Power, then Stamina, then Regen. Power is essential for reaching lower depths without burning out your stamina. Regen is not too noticeable until you get at least 8-10 points in it, but by that point you are already at endgame and may have already reached water anyway.
2. Best boots is Snow boots. Magmawalkers have overly low stamina, and will even cost you stamina to equip it in the only layer that it's useful. Magma walkers either needs stamina buffed or to be able to work in both directions, imo.
3. Buy torches, once you reach Ice is when they start becoming useful. Before ice you don't need to use/waste them. Ladders are useful, but don't go crazy spending on them. I personally always have at least 6 torches and 2-4 ladders in my inventory at any given time.
4. Spoiler: The way to get the "mine quartz in magma" turtle is to use sand to bring quartz all the way down to the magma layer and then mine it there. You just keep letting a piece of quartz fall, lets say somewhere in the middle, while continously dropping it by digging under it, just be careful not to accidently grab the quartz., go slow.
5. I haven't found the diamond pickaxe yet, but I have all the other tools. Iron and Titanium pickaxes are the most useful that offer the most usefulness for what you have to spend buying/repairing them. Since iron pickaxe is easier to repair, one strategy for being more efficient with material spending is to use iron pickaxe for the easier layers then switching to titanium pickaxe when you need the extra power in the lower layers. If you don't mind spending extra time farming titanium, then just using titanium pickaxe the whole way is the best strategy. Lumen is a really good pickaxe, but needing to use a amethyst/purple gem to repair it is a big detractor that hurts its utility. But it synergizes very will with caleo and a torch out, so very good for getting high power early. Besides maybe synergizing with the Mistral turtle, I don't think Drills are worth the expense compared to pickaxes.
6. Best accessories that I have used are Sanguine signet, Omnishard, Verdiant Radiance (pairs well with caleo). Winterheart and violetheart look useful, but I haven't unlocked them myself. Gilded Shift and Dwarven Bracer are bad. Resonant Prong useful for farming unlocks mostly, and maybe getting resources, but I haven't used because by the time I found it I already had most of the unlocks. Mageflare rune is useful but too expensive imo, should be 8-10 quartz each.
7. Not all materials can be found in every layer. Another user posted the locations in another comment further down.
8. If you are trying to get a jackpot, save up like 250 quartz first. I actually got 2 jackpots in quick succession this way just by starting with high amount of quartz to spin nonstop.
9. I think the easiest turtles for Reaching water are Caleo and Griddle. Caleo pairs really well with a torch and lumen pickaxe. Griddle pairs REALLY well with omnishard. Magma is a cakewalk with griddle. I feel like if you get lucky with reeler you can also get far. I have had some really good runs with reeler but haven't reached water.
10. The best turtles for farming resources are grampashell and reeler. You should be using one of them most of the time until the time comes to start pushing for water.
11. Nix and Pebble are like the "challenge mode" turtles. I haven't done a run with mistral yet, but I imagine she would synergize well with violetheart pendant and a drill.