well duh it's a class where you use spell and sword

A spellsword is someone who specializes in dealing damage both to spellcasters and muscle heads. Not only that being a spellcaster, although it doesn't completely nullify your needs of potions, it will greatly reduce the use of them as the effect can be fulfilled using spells instead. Being a spellcaster will also make you not really have a natural enemy as you can basically deal the maximum potential damage you want on every single class of opponent.

As a spellsword your journey up won't be an easy one. However, rest assured as it only get easier as you grow accustomed to it. What makes it difficult is the fact that the build of a spellsword isn't really a tanky one at least at the start. But it also doesn't have the biggest DPS. This however will change, as soon as you've got yourself some proper spells and equipments. And here is what you need for them

As a spellsword you won't really be tanky. Spellsword is more of a damage dealer that specializes in both against nerdy spellcasters and muscle headed ♥♥♥♥♥♥♥♥. So you will want to invest more into stamina and magicka. You can leave your max HP at 300 or 250 and even out the magicka and stamina. Although I said even out, it's better for you to prioritize magicka over stamina. The reason will be explained below.

The spell class you're mainly gonna use are destruction and restoration. You will want the choking grasp all the way to touch of death. Trust me once you've gotten a grip on this sweet sweet nectar you won't settle for another ♥♥♥♥♥. The damage of that spell is not much but what we're truly looking for is the HP absorption. As a spellsword you'll be fighting at close quarter, elemental spells won't do you much justice except for shooting down airborne dragons. With the touch of death you'll be fighting while absorbing the enemy's health, healing your own health. This will also leave you the trouble of having to switch back and forth from destruction and restoration. But what if the enemy dies before they restore your health to full you say? Well, in that case it's time to suck the life out of your follower. This spell is also unaffected by wards, therefore you can just suck the life of every wizard you see. The restoration spell is useful for its wards which I'm sure you don't use very often since alteration is a wonderful way to keep the damages away. However, you will find it really useful early game as a spellsword against wizard. Because you basically won't have any resistance against elemental damages. The healing spells will also be in use a lot in early game because I can't really say that the choking grasp is that nice of a spell. However as you level up and you reach Touch of death, you will finally be able to taste that sweet blood that comes from you enemy's vaginas.

Eh use whatever you want that suits your style as long as it's one handed, not a dagger and not a fist

You will want to use heavy armor as a spellsword this will save you from needing to use alterations spells to repel damage. And of course enchanted equipments is really important as a spellsword. You don't need to worry 80% in all elemental damage resistances is all you need to have a smooth sailing spellsword playthrough. You can put it on your ring, necklace and boots.

You will want a tank as a follower preferably Russian because you know "cold". This is very important especially in early game where you're basically a sack of meat waiting to be sliced through. However, once you have the equipments, spells, and enchantments you needed. You can have any follower you'd like.

Playing as a spellsword is really fun as it's kinda more diverse than just slashing your way through a dungeion while chugging down potions. Or just sneaking your way through a dungeon like ♥♥♥♥♥♥' hell "A SHAMEFURR DISPLAY". Or roleplaying gay merlin. In addition to all the spells that you're gonna mainly use, you can use other spells from whichever school of magic you'd like. For example invisibility for if you're playing through a thieve's guild questline etc.