Flat terrain 0 energy
1 level up or down -0.9 energy
2 level up or down -3.6 energy
3 level up or down -8.1 energy
etc.

It's much more efficient to go up and down in a staircase path 1 level at a time, but you need to manage this yourself since it's one of the skills of the game. The pathing won't do it automatically.

Dangerous terrain isn't too much of a threat as the danger events are fairly rare and often don't do any health damage. The worst one is a type of smooth snow that will always drain an additional 8 energy, this should be avoided as much as possible.

Night time will drain a lot of warmth. 5 points per hour on normal, and a whopping 9 points per hour on insurmountable difficulty. Over the 12 hours of night this is 60 points of heat loss even on normal. Caves and tents are very valuable especially on higher difficulties because if you rest in one at night 10 hours of this penalty is negated, plus they restore 35 energy.

Based on shrine rewards, energy and warmth are worth 1 point, sanity 3 points, health 15 points.

Since oxygen bottles are so big oxygen is about 2 points.

An hour at night will cost you 5 warmth on normal, if you average this over the day then 1 hour costs 2.5 points on normal, and 4.5 points on insurmountable. When evaluating detours make sure you use this average heat loss, not the current heat loss. On higher difficulties when given a choice the lower time option is the better choice.

Experience points have diminishing returns, they are great at the beginning of the game and much less useful at the end.

Caves. It's worth a large detour to rest in a cave at night, if you are low on tents. Not true in the death zone. They also have mini events that restore 2 points of sanity on average and very rarely a piece of equipment. The darkness event will allow you to convert a torch into 2 cans of food.

Wonders. These give 20 sanity, which is great unless your sanity is full. They are worth up to a 60 point detour.

Shrines. These give either 30 energy, 30 warmth, 10 sanity or 2 health. They are worth up to a 30 point detour.

Treasure chests. These can be highly variable and can be negative, but there is a small probability of getting a tent which is worth a lot. They are worth about a 10 point detour.

Encounters. Pretty similar to treasure chests except they involve interacting with a person or animal. Also worth up to a 10 point detour.

You should try to enter this zone on full energy, especially if you are low on oxygen tanks. Resting and event choices that drain time are not worth it. Detouring to POI's should take into account the oxygen cost at 2 points per oxygen.

Roughly rated from best to worst:

Steep climber. Alpine style is a time saver which is important on high difficulties. The main feature is On the edge which is an extremely powerful activated ability that can break the game.

Consumables expert. Early sleeper gives 10 bonus energy every time you wake up. First aid (4 time for 2 health) is great, especially when you're in a critical state.

Event expert. The abilities are fairly weak. Meditation is excellent though and makes up for it, particularly when you're in a critical state. It can restore health, sanity, energy and warmth in exchange for time.

Extreme geology. 2 levels of one with stone gives you +2 warmth per hour when on stone, and stone is very common. 2 levels of adrenaline can give 30 energy on every bad terrain event which converts bad terrain events to a positive not a negative.

Flat terrain expert. Excellent on low difficulties as this can reduce energy usage by 1 for every move, meaning moves of 1 elevation cost no energy. However on high difficulties you need to rest at night so it's mostly wasted. Careful steps is bad and even worse on high difficulties.

Night climber. It's excellent on normal because it can almost negate heat loss at night, meaning you don't have to time your rests for night anymore. On higher difficulties it doesn't help enough, night is still too deadly and has to be avoided.

Neutral. You can always choose from this tree which is why I'm putting it last. Refocus is good, 4 time for 10 sanity. One level of inner fire (restore 0.75 warmth per hour while moving on any terrain) is also better than most specialised abilities. Acclimatised is even better (+1.5 warmth per hour if it's cold). +40 max oxygen is like an extra oxygen tank when you enter the death zone and an excellent pick.

WARNING This is where you can get pretty cheesy to the point of breaking the game.

It is entirely possible to complete the game on normal without ever entering a critical state. This probably shouldn't be considered part of normal play. You will get a score bonus at the end of the game if you never enter a critical state. Maybe if you are super skillful you could avoid critical states on higher difficulties.

When you enter a critical state, bad things only happen when you are moving. If you are staying still then nothing bad will ever happen. This allows you to do the following cheesy things:

If you run out of oxygen, you can rest to full energy, then use an oxygen tank or the neutral ability breathing exercise to continue. This trick makes the death zone much easier.

If you run out of warmth, then you can use an ability that costs time, or just rest without a tent for the remainder of the night/cold weather. On a non cold morning you will be able to continue. Resting without a tent costs a lot of sanity so the abilities that use time are better.

If you run out of sanity, you can rest to full energy without a tent while insane, then use a herb, or refocus/meditate to continue.

If you have the steep climber ability "on the edge", then any stats can be on 0 including energy, and you can still continue for 4 hours with little cost, including climbing the highest cliffs. For ultimate cheese you can rest without a tent for 44 hours, then trigger the ability again to make 4 more hours of progress with no health loss. This ability can give you a guaranteed win if you're willing to fully abuse it.