From Shinsaibashi station to Osaka Castle

Hello first time travellers to Japan so have a couple of questions TIA

From Shinsaibashi station which train is best for Osaka Castle - and can Suica or Pasmo tickets be used on this line

Also any tips on what else to see in this area eg temples gardens etc

Many thanks Rose

From Shinsaibashi station which train is best for Osaka Castle - and can Suica or Pasmo tickets be used on this line

You can find routes using google map. I did it and found that you can take Osaka Metrofs Nagahori-Tsurumibashi line from Shinsaibashi to Morinomiya (240 yen, 8 min) and then walk (1.4 km, 20 min).

You may better set you accommodation as the starting point so that you may find the better route. In any case Osaka Castle is rather far from any train stations so you need to walk more than 10 min.

Yes you can use Suica or Pasmo IC cards.

Also any tips on what else to see in this area eg temples gardens etc

If you mean gthis areah as Osaka city, it was totally destroyed by the bombing during the WWII (Osaka castle is the exception, but It was reconstructed in 1931 which is just before the WWII). Therefore most of the tourist spots in Osaka are not old temples/shrines but contemporary buildings/museums or boat rides (Osaka is called the city on the water).

If you have one full day in Osaka then you may better consider Osaka amazing pass, 3300 yen one day.

https://osaka-amazing-pass.com/en/

Osaka has some very good places, though in the evening is when the city is at its best. Dotonbori is a lot of fun, and if you want some excellent city views, there's the Abeno Harukas Bldg, Umeda Sky Bldg, Cosmo Tower, and Tsutenkaku Tower in Shinsekai.
http://goo.gl/XE5R94
There is also a TeamLab exhibit in the evening at the Nagai Botanical Garden, though it's far from their best.
In the daytime there is Sumiyoshi Taisha, the Keitakuen Garden next to the Tennoji Zoo, the famous aquarium, and Shitennoji Temple. But if not already in your plans, and you have half a day, I suggest you go to Nara and see Nara Park instead - it has some unforgettable sights, plus 2 gardens - Isuien & Yoshikien - since you express the interest.
https://goo.gl/LfvWnL

Or for Osaka, if you otherwise have too much urban scenery, you can take half a day and go see Minoo Park.

Thank you so much great info very helpful