For a good offensive army, you want to take everything we told you about a defensive army and invert it. Instead of focusing on spamming Guard, you want to spam Warriors. Instead of pairing them with an Eternity Warden, have a Sunblood lead the warriors. Instead of Kroak, use a regular Slann Starmaster. Instead of rounding it out with support for your infantry, you want support for your Slann's casting rolls if you have the points to spare.
One of the biggest differences here is that your saurus leader, unlike the Eternity Warden, has a Command Ability. And importantly, it's a very good one. Making your Sunblood your general instead of your Slann may seem weird at first, but the Sunblood's ability is ideal for systematically wiping out units. Just pick an enemy unit, get rerolls against that unit, ruin that units day with all your firepower, then pick the next unit. You want to use this ability to break down your opponent's lines one unit at a time. Of course it goes without saying, keep your Sunblood out of combat. A total tank he may be, but you need that Command Ability for its brilliant power and if he dies then you lose it forever.
The rest of your army is not so irreplaceable. Your Saurus will die. A lot. But that's okay because unlike Guard these guys are easy to summon. A basic summon will net you ten back from the grave, but if things start getting out of hand then you want to be able to summon 20 with the upgraded spell. Rolling high enough for the upgrade can be a challenge, but there are a lot of modifiers to take advantage of. Firstly making use of the Sage's Staff constellation is great because that nets you an auto +1 to all Casting, and the Great Drake constellation is useless because your Sunblood should already be netting you rerolls To Hit. A Starseer also works great as a supporting mage, using its Curse of Fates on the Starmaster to net it another single-use +1 modifier to any roll, best used on summoning (and the general rerolls you can get from the Starseer's Cosmic Herald ability is useful in any army.) If you can find the funding for an Astriloth Bearer then you get another +1, while the Astriloth may seem rather weak as its rerolls To Hit are useless as the rest of the army will run out of range and the Sunblood grants them anyway, the +1 To Casting that it globally gives to your army is actually very powerful as it goes on to stack with the rest of the modifiers you're getting. Lastly, and this one is down to luck, but if you can find some Arcane terrain then you can camp your Slann on top of it for a final further +1. This adds up so that instead of needing an 11 to summon 20 Warriors, you only need a 7. When you factor in the rerolls that the Starseer can give you for your casting, this becomes relatively easy to pull off, allowing you to just resummon your hordes faster than your enemy can kill them. Not to mention that the Astriloth bearer grants bonus spell range, allowing you to summon and support your front line from much further away.
If you can afford it, an Eternity Warden can be of great help to safeguard your Slann. While it may not do as much as it does in a defensive army, it can be resummoned if it dies and can really save your Slann's neck if somebody tries to cut your summoning off.
Finally, it's debatable on whether or not you should take the Sunclaw Starhost battalion. Personally I'd recommend against it as it forces you to divide your troops up into smaller units that will likely get killed very quickly anyway because you expect your Warrior to die like Skaven because they can just be resummoned, which loses them the Sunclaw buffs anyway. While in a bigger unit they can net their horde bonuses with the Ordered Cohort ability, getting bonuses To Hit and even to their Attacks if you have enough. Oh, and I'd recommend spears for them, you may find it harder to wound but the extra range will let you make more attacks, and the rerolls that the Sunblood offers makes extra attacks very desirable, but that's a more debatable choice, you should be fine with either. And don't forget that a Mystic Shield can do wonders for your Warriors, that +1 Save will make a huge difference and their shields are very powerful once you hit a 4+ Save. Oh, and don't forge the Wardrums. Every unit must have Wardrums, they will be how you make it across the battlefield to catch your enemy.
, I could bring a few painted models for you to look at.