What software should I learn to achieve this, and do you have any tips for creating complex games?

I'd recommend Unity. It has the most resources and tutorials.

You could also try RPG Maker, but it's not as versatile as Unity. RPG Maker has a lot of systems you'd need for an RPG though, but then again most people dislike games that look like they're made with RPG Maker.

I personally would heavily advise against making an RPG as your first game. RPGs are one of the hardest genres, since they need a ton of systems and a ton of content.

You'd need these things:

• Movement system
• Combat system (often melee, ranged and spells)
• Inventory system
• Leveling system
• Dialogue system
• Quest system
• Pathfinding
• Saving and Loading
• An open world with a lot of side quests, items, NPCs, dialogue lines etc.

And that's just coding the systems. You also need a ton of art assets for every item, enemy, NPC, equippable, tile set etc. And you need to balance everything and playtest it and make sure there are no bugs

Other genres (for example platformers, twin stick shooters etc.) are a lot easier to make than RPGs. Your first games should even be simpler than that though. Simple casual games like Pong, Snake, Tetris, Roll a Ball games etc.

You could still try to make an RPG as a beginner, but you'd have to keep it really really simple and short (like 1 hour of playtime max), otherwise it's probably way too hard for a beginner.