Welcome back to the hobby! I took a 20+ years break myself. If you really want to learn, I would recommend you to read as much as you can here in Figures forum. Posting your work if you are not too shy and the guys will come to help you.
I hate to disappoint you but Tamiya figures are not exactly the best out there in the market unless it is recently released (not re-boxed) but it is a perfect opportunity for you to tune up your skills before you build better figures.
For the figures, I use:
- Excel knife... best tool! Probably the only one other than paintbrushes. Not just for cutting, but to scrap seams off using the back of blade. Tamiya figures are full of those!
- Liquid plastic cement not in a tube but in a bottle it is too messy for my taste. I like Tamiya Extra Thin.
- Srue cutter (very good one) is nice to have for cleaner cuts if you are willing to invest.
- Super glue is a must if you want to glue non-plastic on the figures. I use thick super glue like Zap-A-Gap to fill in gaps.
- Putty is necessary if you want to change positions of arms & legs.
- Sandpapers, of course! I buy sandpaper files from a local beauty shop as it is alot cheaper and stronger.
For the paints, you need to look at your figures instructions to create a list of paints you need to use. I don't know what kind of paints you can buy in Brazil. I assume Tamiya paints are readily available and it will be easier for you if you are building Tamiya figures. You will see Tamiya paint codes on the instructions.
Hope this helps... just read the posts you will find plenty of useful information. And watch out for Manny...