Alright, I'm having an issue making custom spells. Looking to do this:

Shock Damage 20 on target
Weakness to Shock 100% on target
Weakness to Magic 100% on target

Or something of that nature. I make the spell, cast it at the nearest mage (hey, gotta try it on SOMETHING) and all it seems to do is tickle them. I've tried the same with touch, and all I get is a tickle unless I nail them twice quickly. What am I messing up? I'd love to make a few spells the from a distance I can blast something right off the ground (and kill it)

The weakness part of the spell only takes effect after the damage part. You need to put a duration on the weakness part, like 2 or 3 seconds, and you can hit them a second time while they're weak.

Ah, I see...thats kind of a bummer. They kinda notice when the first one hits them, would be hard to hit them with a second one on the move.

Depending on the distance, I've found that I can often get off a second shot even before the first one hits. There's also a momentary delay, before they realize they're hit.

Not sure what levels you're working with... At high enough levels, with enough magicka, you can start with a Paralyze, which will knock the target down. Also, if you've done the Knights of the Nine, you have Drain [Attribute] available; Drain Speed can be added into your spell to slow the target down.

Now to be real nasty add drain health 100 for one second in the beginning and you do some real serious damage, first hit do 20 in damage and drain 100 so you kill anything with less than 120 hp, second hit does 40 in damage and drains 200 so you would kill anything with less than 260, if that is not enough the next hit kills them.
Use that spell myself but with 25 in shock damage. Remember to block with your weapon then casting, as you cast faster, still nice with 2-3 seconds duration on weakness if you miss with one spell.
You can use this effects on weapons to.
I always use ranged magic for all my combat spells, hold down block and cast 2-3 or perhaps 4 spells at target. with fire effect spells its pretty common that all the spells are in the air before the first hit, combine this with detect life 150ft and you want to increase the difficulty.

If you hold down the block button, when casting a spell, you can fire that spell (provided you have the magicka for it) very fast, repeatedly. You should be able to get off three if not four casts while holding the block down. If you extend the weaknesses out past one second, that second cast that successfully hits will be a doozy.

I save my game before I create a spell, then fast travel to that one starter cave on the island itself. I test it out on the bandits there. If I screwed up, I reload my save, and try to get a better combination of effects. Or, test it out on the apprentices outside. It's hard to get an idea of AOE spells outside with the apprentices, hence why I fast travel to a cave to test those kinds of spells I create.

Options to consider:

A modest radius of effect means the target can move a little and still get hit by the first shot. The negative side of that is more cost and inability to use the spell close to allies. Since the majority of the cost goes into the weaknesses, the cost of the damage part is not too significant. If you're sneaky and they don't see it coming, that's not an issue.

Slowing the target's movement, or even using paralysis, can make it easier to hit them with the second shot. It only has to last long enough to hit them again, so it can be a cheap addition to the spell.

You trade-offs here are total magic drain against the chance of missing. Fortify Magicka can make the spell sustainable, but when you stop casting, you're probably on empty. That's OK for a final boss, as you'd have plenty of time to charge back up.

How does magick stack in Oblivion? Like say, a list of spells combined together...oh, for example...:

Fire Damage 20 pts on strike
Frost Damage 20 pts on strike
Weakness to Magicka 100 for 2 secs on strike


What would happen first? The fire damage? or the Weakness to Magicka? How would you make it continuous?

What do you mean by continuous?
It would happen in the order that you have it, however the animation would be a shock spell, as it is the highest cost (in terms of magicka use) of all the effects.
To, what I think you're asking about continuous, make a different spell like this:

Fire Damage 15 points for 2 seconds on target
Shock Damage 15 points for 2 seconds on target
Weakness to Fire 100% for 6 seconds on target
Weakness to Shock 100% for 6 seconds on target
Weakness to Magic 100% for 6 seconds on target

The second cast would hurt a lot. If you change all effects from target to touch, the magicka cost drops dramatically, as well as the added benefit of making higher damage with less time, because you should be able to hit them faster.

In Oblivion weakness is not applied before the second time you cast, believes they are cancelled if you putt them before the elemental effect. This is different form Morrowind where you could use a weakness to fire+ fire damage for double effect.

Has no success with fire damage + weakness to magic work in theory it should work however my test showed that it did not work well, however the combination fire damage+ weakness to fire does double damage on the second hit.
If you use fire damage + weakness to fire + weakness to magic you get a doubling of magic damage each hit as long as you hit before the weakness effect times out. Yes this will cut down enemies an enemy with twice the hp survives on hit more, an enemy with immunity to the elemental effect also survives one more hit as the first strike just compensate for it.

With continuous I assume you are thinking about adding fortify magic at the end of the spell.
I’m interested myself as my first test did not work and my second test was interrupted by a helpful and topless mage.

Might be that fortify magic on self don’t work then added on an on target spell because of the delay before hit? Does anybody know?
Prefer on target spells myself, keeps the vulnerable mage out of harms way.