A lot of the Lord of the Rings and Hobbit models are fairly simple to assemble, because they were sculpted in one piece. Even the larger models (cavalry, trolls) are generally only in a few pieces and relatively easy compared to some other models. The Lord of the Rings range is a little older and probably a little easier to assemble in general, though the figures are still very characterful.
There's a mix of materials that models come in. They could be in metal (older models and some re-releases), "finecast" (some Hobbit models), resin (some re-released models and Forge World models like the Iron Hills dwarves) or plastic (lots of the basic box troops). Metal/finecast/resin you can glue with superglue and plastic with plastic glue. The finecast/resin models take the most clean-up ... some of the models were originally done in metal, then re-released in resin and these need some work with a knife to scrape off spare material/tabs.
The plastic infantry boxes are probably a good place to start if you're new to modelling. Getting some clippers is much easier/safer for taking stuff off the sprues than a craft knife.
You can buy glue/craft knives/clippers etc. in many places, or all on the Games Workshop website. Games Workshop also has a nice range of paints that's good for beginners. Start by painting base colours, which are thick and cover the model well. Then you can add layer colours on top as highlights. And using a wash (aggrax earthshade/nuln oil) to put a bit of shade in can instantly transform a model.
https://www.games-workshop.com/en-GB/Ci ... aint-GuideGames Workshop does loads of painting videos on YouTube that would show you techniques you can use (although mostly not using LOTR models). If you live near one of their shops they might do lessons too.
If you don't want GW paints, another range you could try is Army Painter, available in lots of online stores.