You could just download the Vendor tools (Xilinx, Intel, Lattice) and start with simulations. They are usually free of charge for private use. Often including their smaller chips. For Xilinx you could, for example, get the Digilent Arty-A7 board, which is based on Xilinx' Artix-7 chip and has plenty of space. There are also free tools for Simulation like GHDL+Gtkwave, but i am completely unsure if there is any that lets you do HLS

FPGA hardware is expensive though