The Tokina AT-X Pro 100mm f/2.8 is one of the most affordable macro lenses. It's quite capable of making fine images, but is pretty basic.
IMPORTANT: If you are planning to use on a Nikon camera, be aware that the version of the Tokina lens in that mount does not have an in-lens focusing motor. Notice the "D" designation Tokina uses. IT WILL BE MANUAL FOCUS ONLY on many Nikon cameras, including all the current and recent D3000-series and D5000-series models. It uses the "screw drive" like some Nikkors (such as "AF"... not AF-S or AF-P). This is only able to auto focus on cameras with the focus drive motor built into the camera body itself, i.e. D7000-series and higher current/recent models.
It may or may not be a "deal killer" for a macro lens to be manual focus only. Much macro shooting is more easily done with manual focus anyway. However, especially if you plan to use the lens for other things, as a short or moderate telephoto for non-macro work, you may not be happy with it.
Tokina AT-X Pro lenses are generally well made. They do use a unique "focus clutch" mechanism (in all mounts, not just Nikon). To switch from auto to manual focus and vice versa, you slide the focusing ring slightly forward or backward. When it's set to auto focus, no manual focusing is possible. The focus ring is disconnected from the mechanism and merely turns, doesn't change focus. As a result, you cannot manually override and "fine tune" autofocus... you first have to "shift" the lens out of auto focus mode. This is done to protect the "micro motor" focus drive the Canon mount version of the lens uses (no motor at all in the Nikon mount version). Nikkor AF-S and AF-P, Sigma HSD, Tamron USD, Canon USM and STM focus drive lenses all allow "full time override" of AF... no need to turn it off first. Like Tokina, they all also use micro motor focus drive where this is not possible, usually in their most entry-level, lower priced lenses.
The Tokina macro lens also is not "IF" or "Internal Focusing". This means the length of the lens increases as it's focused closer (all mount versions). In the case of a macro lens, the length increases A LOT! It almost doubles in length by the time it's at full 1:1 magnification. "IF" lenses do not increase in length (Micro Nikkor 105mm VR, Sigma 105mm OS, Tamron 90mm VC, Tamron 60mm, Canon 100mm USM, Canon 100mm f/2.8L IS USM are all examples of IF lenses. The ealier Nikkor non-VR and the cheaper Tamron 90mm non-VC are a couple examples that aren't IF.)
The minimum focus distance (MFD) of a lens like the Tokina 100mm is about 12". But lens MFD is measured from the film/sensor plane of the camera.... so part of the 12" space is occupied by portions of the camera and the lens itself. MFD is not the same as "working distance", which is measured from the front of the lens to the subject. At it's highest magnification, the Tokina lens has only about 4.5" working space (without it's lens hood mounted). IF lenses that don't grow longer when focused closer start out a little bigger (and actually change focal length slightly, though you don't really notice it when using them).
The Tokina lens has a "simple" Focus Limiter with two ranges: "full" and "non-macro only". Some other, more advanced lenses have three range limiters, usually with "full", "macro only" and "non-macro only". Focus Limiters can be used to help speed up lens focusing. They are common on macro lenses, which tend to be slower focusing than other types of lenses. Due to the very shallow depth of field that's rendered at high magnifications, most macro lenses' focus mechanisms are designed to emphasize precision, over speed. They also have to move their focusing group a long, long way to go all the way from infinity to full 1:1 magnification.
In the end, the Tokina 100mm Macro has some limitations, but is quite capable and is one of the most affordable of macro lenses. It's been around for a long time and lots of people are happily using them.
100mm (or close to it, such as 90mm or 105mm) is what I normally recommend for people considering their first macro lens. Shorter focal length macro lenses such as 60mm, 50mm or less put you even closer to subjects, which can be a problem with live subjects or might cause you to cast a shadow over other subjects (but can be useful for indoor/tabletop studio type work). Longer focal lengths macro lenses such as 150mm, 180mm or 200mm are more difficult to hold steady and render very shallow depth of field (but can be useful for particularly shy live subjects... or those that bite or sting!)
Personally, for close-up and macro work I have 45mm, 60mm, 65mm (an ultra-high magnification lens), 90mm (compact, vintage manual focus), 100mm and 180mm lenses. I also sometimes use 70-200, 300mm and 100-400mm lenses which have close-up abilities.
My most-used "serious" macro lens is my Canon EF 100mm (on both crop sensor and full frame DSLRs). The others tend to be used for more specialized macro/close-up situations.
There are a number of online reviews of the Tokina 100mm Macro lens:
https://kenrockwell.com/tokina/100mm-f28.htm (On Nikon cameras.)
https://www.the-digital-picture.com/Reviews/Tokina-100mm-f-2.8-AT-X-Pro-Macro-Lens.aspx (On Canon cameras... no extensive review, but image quality, specs and sample images available).
https://www.dxomark.com/tokina-at-x-m100-af-pro-d-100mm-f2-8-nikon-mount-lens-review-excellent-all-round-performance/https://www.grantatkinson.com/blog/tokina-at-x-pro-macro-100-f2-8-d-field-review (Canon mount version.)
https://www.imaging-resource.com/lenses/tokina/100mm-f2.8-at-x-100-af-pro-d/review/https://www.dpreview.com/products/tokina/lenses/tokina_atx_100_2p8_macro