Tofugu’s 4500 Sentences

Although, I’d say, going for the actual (low level) in-context reading, like Japanese Graded Readers, is the best; I myself have created a reading speed test, along with comprehension test, here – How many sentences (by JLPT) can you read in 1 minute? Let's read Japanese sentences with self-checkable translations. [Anki/Spreadsheet/Desktop app] - #6 by polv

Let’s go for at least 10 sentences per minute, with like 90% comprehension rate. Let’s see if you can go there for N3 with Kanji level 100.