You have 2 main pathways for building on FVM:
1. (available sooner) Building an EVM smart contract that then interfaces with Filecoin's built-in actors. This will use existing EVM smart contract dev tools like HardHat, Truffle, Remix, Metamask, etc - and most contracts will likely be written in solidity (or any other EVM compatible language)
2. Native Rust smart contracts (or any language that compiles to run directly in the wasm FVM runtime). There is less tooling available for this today (though there are a few WIP SDKs being built in the Early Builders program), but maybe more accessible if you don't know solidity.
You can look for some of the FVM Foundry demo videos to see what folks are building so far! https://www.youtube.com/watch?v=jTtZh1zqUr8