I would go with the Groove trainer next as it gives you lots of little etudes (studies) for you to practise on but doesn’t have all that much theory. Depends to some extent on what you are looking for. Do you want to learn more music theory? In which case some of the Talking Bass theory courses like Chord Tone Essentials would be ideal or for more practice oriented stuff the Groove Trainer would be good.
Another thing that will develop your playing no end, having completed B2B, is get into doing covers. Loads of help on this forum about ways to get your favourite songs, find the tab/music online and create backing tracks with the bass removed. Then you can record yourself playing them (also loads of help in these pages) and join in the fun on the Covers thread: Post your covers! (2024) - #2885 by TheMadBassist
Given your financial constraints another alternative, but a little less structured, would be to get into all the free lessons both Josh (B2B) and Mark (Talking Bass) have on their youtube channels.