I am not a lawyer. This does not constitute legal advice. If you need legal advice in a practical matter, get a lawyer. Yadda, yadda.
However, these are two well understood parts of game design, so I can comment in general.
Rules cannot be protected by copyright, as they are procedures and processes. The appropriate area of government production monopoly for procedures and processes is patent law. However, the US Patent Office has stated that the rules of the game cannot be patented in the United States. Other countries will be different, but the rules of the game are unlikely to grant patent protection for similar reasons.
Words ("expression") can be protected by copyright. Never reuse words from another game, book, TV show, etc. without written permission or license agreement. Copyright only applies to expressions of ideas, so it only covers text lengths (although the length can be quite short, like the 140 letters of the text). 39; a tweet). Copyright applies to any work, whether or not it has a copyright notice – it is automatic in most jurisdictions. The more unique and recognizable a given combination of words, the less sure you are of using them.
It should be noted in particular that tables are widely regarded as an "expression" of an idea, so game designers avoid copying them even when there is no such thing as 39; another way of representing a set of mechanical details. This has not yet been tested in court, but no one wants to be the first to discover the difficult path. If you look at various D&D dummies such as OSRIC or Lord of the Labyrinth, you will notice that the XP table numbers do not match the originals. It is deliberate.
Individual names or recognizable terms can also be trademarks, but this only really happens with big game brands, as it is expensive to apply and apply for trademarks.
Individual words or compound terms can be authorized in a so-called nominative use where you simply indicate the name protected by copyright by someone else, but this is delicate terrain and if you want to attempt a use registered, you must speak to a lawyer. Individual terms that are generically descriptive also do not benefit from copyright or trademark protection, but you should be sure that the term is generic and is not specific to this expression of the rules.
This division is generally summarized in the game design community as (paraphrasing) "the rules of the game can be copied, but their expression – the words used to convey them – cannot be copied."
Game designers use rule templates from other games all the time. Good designers rarely copy exactly however, because good designers know that a rule is almost never going to adapt to other, different rules, unless it changes to suit them better. However, when direct copying is done, it is completely legal and generally not even a point of professional conflict, as the rest of the game design will be different and the overall game will be something new under the sun. We all love to see new games.
Some designers will quote their inspirations directly in their book. Readers will likely notice similarities anyway, and why not spread the love of games the designer likes?
However, all of this is very specific to games that are released without a bundled license, such as D&D and other games that are released under the Open Games license or one of the Creative Commons licenses. It’s always everything true of games that come with a license, but there are other wrinkles to deal with.
I notice that you are talking about "gifts", "classes", "spells" and "skills". These four elements taken together indicate to me that you plan to use the rules of one of the editions of Wizards of the Coast Dungeons & Dragons. In this case, you must be extremely careful. The 3rd edition of the game is under OGL license. It gives you permission to use various parts of the system and nomenclature that you wouldn't normally be able to use without worrying about legal action, and in exchange, this requires additional restrictions that copyright / trademark / patent does not normally impose, such as avoiding certain terms. But more importantly, WotC (Hasbro) is a big fish in a small pond, and even the legal uses of D&D products will likely catch their eye. do not accepting their OGL license for the release of a large-scale game or product is a good way to get their unfortunate legal attention, even if your use is totally par- overboard. However, using OGL is a good way to play with WotC's toys and have a reasonable expectation of immunity from any legal action. Many game designers have chosen this path.
(The 4th edition is a whole different pot of fish – there is a license, but it is very restrictive. Walk lightly when writing systems inspired by 4th.)
And finally, all of this is moot if you don't publish, design a game for personal use, don't release the game informally, or if you're not or under the radar of the owner of the intellectual property. If you publish it somewhere (for example, post it on a forum or something), there is always an infinitesimal chance from whom you copied and get a legal nastygram, but the probability is low . That's not to say it's a good idea, but rather a comment on the likelihood that the legalities are relevant if you do it for private use or limited private distribution.